Title: STUDY MATERIALS - Pre-press procedure and file validation in practice
Course: Pre-Press Procedure / e-design > Section: Part IV - Pre-press procedure and file validation in practice

After the online lectures, the study materials along with the map of new concepts will be uploaded to Moodle.

Closed format

Closed format

A closed document format means that these file formats are created by a commercial company, usually a software producer, and their source codes are not disclosed to third parties. Different versions of the software with the same name usually use different document formats. For example, changes are made to a document created by newer software that prevents it from being opened in older versions of the same program, or the document is opened with errors. Thus, the owner of such software is constantly forced to spend on version upgrades. Sometimes changes are really innovative and necessary, but in many cases, the financial interests of the software producer outweigh the efficiency offered by the upgrades. Upgrades usually impose more significant requirements for computer resources, which in turn creates additional costs to obtain more efficient computer hardware.

The closed document format is always paid and incompatible with other programs. Recently, software producers have begun to address compatibility in certain common applications. This allows opening some document files generated in different programs with some exceptions. For example, it is possible to open Adobe Illustrator and Auto Cad files in Corel Draw. It is also possible to open Auto CAD files in Adobe Illustrator. However, this may not always work best. It may happen that the files may not open, or some layouts or text may be out of place when you open them.

Thanks to the development of PDF, newer paid programs are able to generate PDF files. However, in prepress great care must be taken when printing with PDF files generated directly from the program. Preferably, a PDF file used for printing must be generated through postscript. Versions that do not allow exporting PDF files meeting PDFX1-a standard from the program must not be used to generate print PDF files. However, even with older versions released before 2008, there may be problems with prepress. The main problems are fonts, overprint and transparency.

Open format

Open format

An open file format means that the structure of the document is in accordance with a standard developed by several companies and public organisations, and the specification is available to anyone. The open file format must be independent of a specific application, manufacturer, or operating system. It must be described in a way that allows full, unlicensed implementation by anyone who wishes to do so.

The use of electronic document formats based only on open standards ensures that the data is usable and accessible to its owners even over a long period of time and without paying royalties to third parties (i.e. the owner of a closed file format).

The need for open document formats was necessitated by the need for countries to provide their citizens with the opportunity to make, send and, today, digitally sign digital documents free of charge.

Currently, such a document format is OpenDocument or ODF (Open Document Format for Office Applications). It was originally developed by Sun Microsystems, but the standard for an open document was developed by OASIS (Organization for the Advancement of Structured Information Standards), which is also international standard ISO/IEC 26300.

OpenDocument is an open file format, which means that the structure of the document complies with the standard prepared by several public organisations and many companies and the software is available free of charge to anyone who wants it. With the open file format, OpenDocument is independent of a specific application, manufacturer, or operating system. OpenDocument is an open, XML-based file format for electronic documents that complies with the international standard ISO/IEC 26300 approved by ISO and IEC.

OpenOffice meets the criteria approved by the European Union for open document formats.

For example, the following office software applications use OpenDocument as a default format: OpenOffice.org, Sun Star Office, IBM Lotus Symphony, Google Docs, KOffice, NeoOffice, Mobile Office. OpenDocument support is also available for many other software applications: IBM Workplace, IBM Lotus Notes 8, Corel WordPerfect Office, EIOffice, Co-Create Office, Abiword, TextEdit, TextMaker, Gnumeric, Scribus, etc., also Microsoft Office starting from version 2007 SP2.

Commonly used OpenDocument file extensions are for example:

    - .odt - text documents
    - .ods – spreadsheet
    - .odp – presentations
    - .odg graphics

PDF open document format

Open document format PDF

Document format PDF is an open standard developed by Adobe Systems for platform-independent distribution of electronic documents. It became an ISO standard on 1 July 2008 - ISO 32000-1:2008.

In other words, PDF is a universal file format that – it retains the original appearance, format, graphics, and colours of the original document, regardless of the platform and version used (both hardware and software). Thereby it is ensured that the appearance and layout of the page is always the same on the screen and printed on paper, regardless of the type of the printer used.

In addition to text and graphics, a PDF document can contain references, indexes, hyperlinks, active form fields, and other (interactive) elements. PDF files are compact and there are no restrictions on their distribution, browsing or printing. PDF readers corresponding to the open document format are Adobe Reader 8.0 and later, which can be downloaded from here http://www.adobe.com/.

Summary

PDF files can be read by anyone – the reading software is free. Creating a PDF file is quick and easy. PDF files are small in size (so they can be transmitted faster over the Internet), and the format of a PDF file is always the same everywhere (this makes PDF a suitable format for archiving documents).

Postscript

History of POSTSCRIPT

John Warnock founded the PostScript programming language in 1976 at Evans and Sutherland.

John Warnock

In 1978, Warnock joined Xerox PARC and developed a design system called JaM with Martin Newell. Its further development is known as InterPress. Warnock co-founded Adobe System with Chuck Geschke in 1982. In 1984 they introduced a simpler language based on InterPress called PostScript, adapted for laser printers. In 1985 the first PostScript-enabled laser printer (AppleLaserWriter) was introduced to the market. Since then, the use of PostScript has become common in laser printers. As of 2001, the use of postscript support in printers was no longer important, because it was cheaper to write a document as a postscript in the computer than to add postscript support to the printer.

Programming language

The PostScript programming language is a system based on a stack (the data structure where the last entry is read first). Typically, PostScript programs are written by other programs, not humans. PostScript can be interpreted by GhostScript and the Acrobat Distiller used in prepress.

The PostScript language is distinguished by levels:

    - 1984 - initial PostScript or PostScript Level 1
    - 1991 - PostScript Level 2. Improved speed, JPEG added directly in PostScript, repeating parts of a document

1997 - PostScript Level 3. Improved colour handling, error handling, program content filters (compression, format interpretation, etc.), structure of the program. More information about PostScript can be read in “The Green Book” .

Postscript file

A postscript file is a file, which is generated through the postscript programming language and is designed to send the required document unaltered to a laser, film or plate printer. All professional design programs used today can generate postscript files. The extension of the postscript file is *.ps, and it can also be identified with the print file *.prn. In addition, we can use the Windows utility PrintFile, which generates print files (a file where files are created for the required printer using a special printer driver). The program recognises plain text files, postscript and EPS files.

EPS (encapsulated postscript)

EPS (encapsulated postscript)

However, there are also postscript files that can be edited during design. These are called EPS files – encapsulated postscript files. EPS is a standard file format for importing and exporting postscript files.

An EPS file is a combination of text, image and graphics. EPS can be made with any design program and is designed to be able to simultaneously see text graphics and images on the screen. As EPS files are relatively large, they are mainly used to design ads. Presenting an entire magazine in EPS is not visible.

An example of how EPS is written

An example of how postscript is written

PDF - portable document format

PDF - portable document format

The further development of postscript is the PDF or portable document format. It is “digital paper’ that is easy to use for viewing on the Internet as well and as a print file for printers and as a digital original. The PDF is obtained when the postscript file is processed with Acrobat Distiller. There are PDFs for on-screen viewing and printable PDFs for printing. Although they look the same on the screen, the process for generating them is different.

Acrobat Distiller

Acrobat Distiller is a program included in Adobe Acrobat Professional that creates postscript PDFs. Until version 1.6, Distiller comes as a separate program included in Acrobat Professional. Starting from version 1.7, Distiller can be opened with Acrobat's own menu options. Distiller allows the settings the user wants to receive PDFs with to be determined. These settings are called joboption. In settings, the user can specify graphic object size, colour space, PDF standard, fonts, Acrobat version, and much more.

Adobe PDF

In 1991 John Warnock, founder of Adobe Systems, described in Camelot the term portable document format for the first time.  Adobe Systems created the PDF in 1993, and Adobe Acrobat 1.0 to work with it is marked as PDF 1.0.

Versions and markings of Adobe Acrobat:

- (1993) - PDF 1.0 / Acrobat 1.0
- (1994) - PDF 1.1 / Acrobat 2.0
- (1996) - PDF 1.2 / Acrobat 3.0
- (1999) - PDF 1.3 / Acrobat 4.0
- (2001) - PDF 1.4 / Acrobat 5.0
- (2003) - PDF 1.5 / Acrobat 6.0
- (2005) - PDF 1.6 / Acrobat 7.0
- (2006) - PDF 1.7 / Acrobat 8.0
- (2008) – PDF 1.7, Adobe Extension Level 3 / Acrobat 9.0
- (2009) – PDF 1.7, Adobe Extension Level 5 / Acrobat 9.1
- (2011) – PDF 1.7, Adobe Extension Level 9 / Acrobat X.

The development of PDF has been diverse and it is used in many areas. However, PDFs are not yet so universal that they can be used in the same way in all areas of life. For example, PDFs intended for publication on the web are by no means suitable as print originals. Also, a PDF that is considered an electronic document cannot always be used as a print original. To solve the confusion, standards have been set for PDFs stipulating the requirements for different fields.

PDF 2.0 - a global standard for electronic documents. Read more here!

PDF standards

PDF standards

PDF / X (from 2001 - for ISO 15929 and ISO 15930 series standards) – standard for digital originals used for printing, based on PDF 1.3, PDF 1.4 and later PDF 1.6 versions PDF / A (for standards starting from 2005-series ISO 19005) – for long-term storage of PDFs used for electronic documents, based on PDF 1.4 and PDF 1.7 versions.

PDF / E (from 2008 - ISO 24517) – for PDFs used in construction based on PDF 1.6 version.

PDF / VT (from 2010 - ISO 16612-2) – for data exchange at different speeds in a graphic design based on PDF 1.6 and limited to PDF / X-4 and PDF / X-5 standards.

PDF / UA (under development 2011 - ISO / DIS 14289-1) - PDF Universal Access - Accessibility of attachments in electronic document format based on ISO 32000 – 1 – PDF 1.7 version.

In this document, we will cover PDF/A and PDF/X standards in more detail.

PDF/A standard

The PDF/A standard is intended for managing and storing electronic documents. The standard does not specify the archiving system.

PDF/A is 100% under own control. All information, appearance and form of the document must always be the same as the document itself. PDF/A became an ISO standard ISO 19005-1:2005 on 1 October, 2005.

The standard describes what a PDF/A compliant DF must contain: all content – text, images and vector graphics, fonts and colour information. PDF/A document is not able to handle external programs such as foundation programs or hyperlinks.

PDF/A requirements that a PDF must meet:

    - Audio and video content is prohibited
    - JavaScript and the sending out a destroying file is prohibited
    - All fonts are included and must also allow the ability to include an unlimited number of legal and universal fonts. This also applies to Postscript fonts Times or Helvetica
    - Colours are determined independently of the output device
    - Encryption is not allowed

PDF/Al has two levels: PDF/A-1a – Level A contains all the requirements, and PDF/A-1b ensures that the document structure is included. It must be possible to search and sort the contents of the document.

PDF/A-1b – Level B ensures the preservable visual appearance of the document. There is also a new version of PDF/A-2. It works on version 1.6 (Acrobat 7.0).

In the case of PDF/A standard, it is possible to use both CMYK and RGB colour spaces in PDF.

PDF/X standard

PDF/X standard, that contains various ISO standards and requirements for PDFs that are used in graphic design and prepress and that are not allowed in a standard PDF.

Basic requirements for PDF/X files:

    - PDF/X1a requires that all fonts are included and that images are in CMYK or spot colours. DF/X files contain colour management information and own colour profile is included. For example, even if the file is made in CMYK, the illustrations may be in RGB (with calibration information).
    - Different files (boxes) must be defined in PDF/X compliant files. Media Box shows the size of the document.
    - Trim box shows the clipboard or final format. When printing with a bleed, the Bleed Box must be larger than the Trim Box but smaller than the Media Box.
    - Active content is not included in PDF/X. This means that while annotations, comments, sound effects, and even movies are allowed in a simple PDF, they are not allowed in a PDF/X.

Different versions of PDF/X standards

PDF/X-1a:2001 (ISO 15930-1), recognizes only CMYK + Spot colours, based on PDF 1.3.

PDF/X-2 (ISO 15930-2), it deals with PDF files that may not contain all components, for example, fonts and images may move to the destination separately from the PDF file for various reasons (copyright, file size, workflow, etc.); PDF/X-2 must be compatible with both PDF/X-1 and PDF/X-3 standards. This standard has never been used.

PDF/X-3:2002 (ISO 15930-3), recognises CMYK, Spot, managed by RGB, CIELAB, with ICC profile, based on PDF 1.3 version.   Suitable for applications where the printing process is unknown at the time the file was created (such as an ad that goes to multiple newspapers at once) or where colour management is used.

PDF/X-1a:2003 (ISO 15930-4), - PDF/X-1a:2001 update is based on PDF 1.4 version.

PDF/X-2:2003 (ISO 15930-5), updated PDF/X-3 recognizes external linked information such as OPI.

PDF/X-3:2003 (ISO 15930-6), updated PDF/X-3:2002 based on PDF 1.4 version.

PDF/X-4:2008 (ISO 15930-7), with colour management, CMYK, grey, RGB or spot data are included, such as PDF transparency and optional content.

For PDF/X-4p ICC profiles are included separately. PDF/X-5:2008(ISO 15930-8).

PDF/X-5g is based on PDF/X-4 version and allows combining OPI and external graphical information.

PDF/X-5pg is based on PDF/X-4p version and allows adding external graphical information and an ICC profile.

PDF/X-5n is based on PDF/X-4p version and allows adding an ICC profile for colour spaces other than Grayscale, CMYK and RGB.

Normally PDFX/1-a:2001 or PDF/X-1a: 2003 standard must be used, which guarantees that there are as few problems as possible with the colour separation in the RIP during prepress.

PDF creation

Adobe Acrobat

The role of Adobe Acrobat in the CS product family is to view, create and manage PDF (Portable Document Format) files. Unlike the free downloadable Adobe Acrobat Reader, which can only be used to view documents, it is a commercial software. Until version 9.0, Adobe Acrobat also included a sister program called Adobe Distiller, which was essentially a virtual printer driver and allowed creation of PDFs with predefined parameters. For today's version of Adobe Acrobat X, Distiller is integrated as part of Acrobat content.

Creating a PDF

A PDF can be created in two ways:

- saving (Ai) /
- exporting (Id) and printing through a virtual printer (Distiller) / distilling from a previously made postscript (ps) file.

The substantive difference between saving/exporting (and distilling) PDF is the method based on the older technology of the latter, where interactive content cannot be added to PDF, colour management workflow is not supported, and transparency is flattened. It cannot be said that one method is better or safer than another, but since we are creating a printable PDF, interactive content is not important to us. Transparency flattening either within the application, during PDF generation or in the print-shop RIP is also not essential for us, and a colour management workflow is not common in Europe (a workflow that supports colour management allows including a Lab or RGB colour space).

Let us take a closer look at exporting from the InDesign program.

Before generating a PDF, we should make sure that our design file meets the requirements. It is important to review the format, the bleed presence, the resolution of the images and the compliance with the CMYK colour space, the number of colours (CMYK + possible additional colours) and all linked files. You also need to be sure of the availability of fonts (licenses). Prepress in InDesign is made easy with the built-in Preflight function, where you can set a control profile that provides the desired information about the file to be checked.

Once we are sure that the file is in print condition, we can start generating PDF.

To save a document as PDF

Select File > Adobe PDF Preset > [PDF/X-1a:2001]

Marks and Bleeds – we see the possibilities of determining the size of the bleed and adding various printing technique marks. First of all, we need to set the necessary bleed and trim marks. The addition of other marks (registry marks, colour bar, bleed marks) is probably not practical, but it depends on the requirements of each printing house.

Colours - in the menu window, we can set a colour profile to which the available colours will be converted. If we did not work initially in this colour space (for example, from RGB to CMYK).

Advanced - in the menu window, we should set the transparency flattening resolution, which is high resolution for the print file.

If conflicts arise, they will be presented to us as an exclamation point inside a yellow triangle. If everything is OK, click Export and a PDF file will be generated in the directory of your choice.

PDF validation

Checking PDFs

Before imposition and making the plate files, make sure that the PDFs used for printing meet the requirements of the printing house, i.e. the PDF offset printing standards.

Main requirements for offset printing PDFs:

- Resolution. The resolution should preferably be 200-300 dpi. This resolution ensures good image sharpness and quality in printing
- As a rule, the colour space must be in CMYK and ICC profiles must not be included. In larger printing houses, where colour management is organised by themselves, PDFs made in other colour spaces can also be used. PDFs must also conform to PDF/X-3 or PDF/X-4 standard. In this case, ICC profiles may also be included.
- Fonts. All fonts must be embedded
- Overprint. Typically, overprint must be set to black text and objects. In special cases, overprint is removed also from black texts and objects. For example, silver, gold, or neon inks should not be overprinted with black, as these inks have a different composition and, in the case of overprint, they mix. Overprint must not be set on white and non-black text and objects
- PDFs generated by means of exporting must be made with the correct settings. It is obligatory to use PDF/X-1a standard for export. PDFs made with other options may have transparency or font problems in RIP colour separation. PDFs cannot be exported at all with versions prior to Adobe CS products or with any other design programs that do not have PDF/X1-a in the selection of export standards. The page sizes in the PDF should preferably be the same.
- Bleed. Designs extending to the cut lines must extend 3-5 mm over the cutting edge. This is necessary to avoid white edges due to fluctuations in cutting during post-processing
- Allowed maximum ink quantity. The recommended maximum ink quantity varies from paper to paper and from printer to printer.

    - Up to 260% of the maximum allowed ink quantity may be used in newspaper printing,
    - in magazine printing (heatset) on covered paper up to 300%,
    - in sheet offset on covered paper up to 340% and
    - on uncovered paper up to 280%.

In fact, the requirements of each printing house are different, so the parameters that need to be checked may be vary!

Checking PDFs consists of two parts:

- First visual checking and
- secondly checking with a special program.

Visual checking

The correct number, size, bleed and overprint of the pages are checked visually. The number of pages must match the order. The size can be viewed with Acrobat if the size is set to be shown in settings. You can also view the sizes of different folders (trim box, bleed box) if they are set when creating a PDF. Checking overprint visually requires great care and knowledge. Special programs that can be used to change the overprint as needed are very helpful. The main problem with overprint is overprint set on light or white objects. As overprint means printing two full colours on top of each other, overprint set to light objects causes unwanted changes in the colour. For example, if you want to print yellow on blue, overprint set to yellow will result in green instead because two full colours will be printed on top of each other. With overprint set to white, the white object is lost altogether because there is no white ink in offset printing and the image becomes invisible on the print. Things get more complicated when special tones (spot colours) and transparency and incorrect overprint settings are used. In this case, the place meant to be transparent becomes white in the design, because the special tone is a covering colour. Many overprint problems can be solved with special programs designed to check and edit PDFs.

Checking with a special program

There are several options here. From Acrobat Pro version 8.0 the program has built-in preflight, i.e. checking system. There are many different profiles (descriptions) to be checked in PDFs. For example, whether the PDF conforms to PDF/X, PDF/A, or PDF/E standard. The choice of profiles contains also mostly used PDF standards for offset printing. For example, newspaper print (coldset), magazine print (heatset), sheet-fed printing. Checking the PDF against the selected profile will result in a report with all the errors and warnings if the PDF does not match the profile. With Preflight you can also make minor changes to make the PDF meet the requirements of the relevant profile. Another option is to use a special program or file management software for checking. There are more and better ways to check and fix files here.

The best and most widely used programs for checking and editing PDFs are Enfocus products. You can read more about them at http://www.enfocus.com. The latest version in use is Enfocus Pitstop Pro.

Enfocus contains the following programs for working with PDFs: Enfocus Pitstop Pro. This is a program for checking and editing PDFs one by one with Acrobat Pro. When you install Pitstop, it joins Acrobat Pro and works as an add-on to Acrobat. Enfocus tools are added to the Acrobat toolbar. Pitstop tools allow you to select, move objects, edit texts, change raster and vector graphics and colours in a PDF. You can open individual images directly from Acrobat to Photoshop and edit and save changes directly in PDF. You can do the same with vector graphics by opening objects in Illustrator. In addition to the tools, Pitstop contains "actions" – commands for making certain changes throughout PDF and "preflight profiles" – profiles for checking. By selecting the appropriate profile, it is possible to check the files. In Pitstop, it is also possible to make such profiles yourself, which are necessary for the needs of this particular printing house. It is possible to add corresponding actions to profiles – commands so that the necessary changes would take place already during the preflighting. For example, overprint changes or changing spot colours automatically in CMYK colour space. Pitstop allows making many changes. However, extreme care must be taken when making changes to the files of the client, as there is a high risk of corrupting PDF or altering unwanted objects. You can't always let Pitstop to set overprint settings. After preflight, Pitstop always reports on the preflight result, describing the errors in the PDF, the warnings and changes made during preflight. Pitstop can be configured so that the report is always included with the PDF, i.e. you can open the report by opening PDF in Acrobat Pro. Such PDF is called a Certified PDF. In the case of a certified PDF, there is a report icon in the Acrobat menu bar. If it is a green check mark, it is a checked PDF that matches the profile, and if it is a red cross, there are errors in the PDF and information about the errors can be found when you open the report.

Checking with Adobe Acrobat Pro DC

The easiest and fastest way is to check PDF files with Adobe Acrobat Pro DC Preflight. The video below provides a tutorial.

Creating a preflight profile

It would be wise to use a profile that is the most appropriate for your printing house included in Pistop, to add features and save your profile based on it. For example, some parameters should definitely be considered.

PS. As a rule, there are detailed instructions on the websites of printing houses, as well as the possibility to download colour profiles corresponding to the papers.

Here are examples from the website of Kroonpress.

Resolution

Although the recommended resolution is over 200 dpi, the profile could be set to display an error message for resolutions lower than 150 dpi. Today, designers use many images taken with digital cameras with resolutions below 200 dpi.

Fonts

The profile must be configured so that if the fonts are missing or incomplete, an error message will be displayed.

Maximum ink quantity allowed

This could be set as a warning according to the requirements of your printing house. For example, the warning could be set to more than 300% for a magazine printer and more than 330% for a sheet-fed offset printer. An action list can be added to the profile. For example, about changing an overprint, or converting spot colours to CMYK if necessary.

Newer versions come with device link profiles, which means that in PDFs with more colours than allowed they can be customised according to the user’s needs. In this case, care must be taken with vectographic objects. For example, 400% of vectographic objects may turn to 100 black or not change at all. In other cases, this command works well. Profiles can be made for different needs and also used for preflighting accordingly.

RIP-Raster Image Processor

RIP is a special module for colour separation, rasterization and plate file generation. Modern RIP includes a selection of different colour separation engines (renderers). The latest is the Adobe renderer Adobe PDF Print Engine. If such a renderer is in RIP, it should also be selected. Adobe PDF Print Engine can also handle newer PDF versions exported directly from design programs.

RIP configuration

RIPs consist of so-called virtual printers and output plans made for each virtual printer. Virtual printers are associated with so-called hotfolders. Separate virtual printers are made for each printing machine. Printers can be made, for example, according to different raster densities, whether a sheet proofing is printed during ripping or not, and so on. Each printing house adjusts these printers to suit their needs. In addition, it is possible to enter different ICC profiles according to which the RIP is set to make colour separation. When sending files to the corresponding hotfolder, RIP automatically starts ripping files with the parameters set to the corresponding folder. The following explains which parameters are set in RIP.

Basic settings:

    - Select separation engine (renderer).
    - The resolution of the plate is set depending on the platesetter or the films used.
    - The raster density is selected according to the paper or printing machine used.
    - The plate size or a plate of the printing machine is selected. From the platesetter management software, a so-called ipr file can be generated, which contains the parameters of all inserted plates. When using this ipr file in RIP, all plate options of the platesetter automatically appear in the RIP plate selection.
    - If for some reason it is necessary to adjust the size of the dots on the plates, then a so-called plate correction is possible in RIP.
    - Colour separation selection. Either all entered sub-colours are separated or converted to CMYK colour space.
    - In addition to colour separation and plate files, you can also make paper printouts or PDF and JPEG files during ripping.
    - Checking settings of RIP files. RIP also checks PDFs for compliance with the standards or settings required by the printing house. It is checked that the images fit on the printing plate or printout. RIP checks if all colours are in the CMYK colour space. ICC profiles must not be included or other colour spaces used. All colour management must be done before ripping. The presence of fonts is also checked. If there are no fonts, ripping will not be not be performed. It is possible to set overprint, check trapping, line thicknesses. Each printing house adjusts the file check settings to suit their needs.

As RIP is very expensive, it is worth thinking about the latest technological innovations and newer software when purchasing or upgrading it, although the initial price may seem expensive. This field is developing very fast and due to the high price, it is not feasible to buy a new RIP every year. The payback period of RIP should be considered 3-4 years. It must also withstand technological development during this time.