Details Matter: Conforming with International Standards for Viewing PDF Files

| No Comments

I recently asked Ali Hanyaloglu, Acrobat Product Evangelist and Leonard Rosenthol, PDF Standards Architect to help me out with an article on PDF standards and the various viewer technologies out there. Here’s what they’ve got to say…

By now many of you would have heard about the standards called ISO 19005-1 and ISO 15930-3 – that’s PDF/A-1 and PDF/X-3 to most of us. These standards take the published PDF specifications as originally developed by Adobe, and then define what parts from those specifications are both required and restricted for specific workflows. That is, the long-term archiving of electronic documents, and the blind exchange of materials intended for press and high-quality printing, respectively. These standards ensure that there are no surprises when the documents are viewed and printed, such as incorrectly encoded or non-embedded fonts, or colors shifting when printed.

For the same reasons, these ISO standards also define how conforming PDF/A and PDF/X viewing applications (called "conforming readers" by the standards) should behave. Adobe Reader 9 and Adobe Acrobat 9 are examples of conforming readers by following all of the rules required by the ISO 19005-1 and ISO 15930-3 standards, including the proper handling of color. Unfortunately, some non-Adobe PDF viewing tool providers may claim to support PDF/A and PDF/X standards when that is clearly not the case. Understanding and implementing document standards like PDF/A and PDF/X requires a lot of expertise, development and testing (and contributions to the open working groups help too!)

To show you how PDF/A and PDF/X conforming and non-conforming viewing applications differ in their display of documents, here is an example test file. A "litmus test", if you like.

The test file is a PDF document that was originally an image of a blue-green bottle and now conforms with the PDF/A-1b specification (Adobe Acrobat 9.x Pro and Pro Extended can verify that for you).

When viewed in Adobe Reader 9 or Adobe Acrobat 9, the bottle appears purple. Note that PDF/A viewing mode will need to be turned on in the preferences, which is the default…

When viewed in a non-conforming PDF viewer, the bottle appears blue-green.

Wait! Isn’t that backwards?

Actually, no. PDF/A-1 (and PDF/X-3) require that an ISO standards ‘conforming reader’ use the ICC profile that is included in the file’s OutputIntent as the "working space" profile when viewing and printing. In this case, the OutputIntent profile isn’t RGB (Red Green Blue) but GBR. So, although visually the file looks "wrong" in Adobe Reader 9 and Adobe Acrobat 9, it is technically correct and displaying the document with the file-specified color space, as defined by the international standards. The same would happen with a PDF/X-3 file.

Non-Adobe PDF viewers that don’t conform to the international standard would ignore the OutputIntent profile and display the document as RGB.

You can download these PDF/A-1 and PDF/X-3 files and test this out for yourself here.
This is just one possible test. There are other viewing requirements that are part of the international standards. This includes ensuring that the embedded fonts in the PDF file are used instead of local, OS, or printer-based copies (for both PDF/A and PDF/X); making annotations read-only and then displaying tool-tips for them (PDF/A); special handling of grayscale information, and more.

What does this all mean to you? Non-conforming viewers are introducing a risk factor to your workflows, and may not be displaying or printing what was originally intended, whether that is now or well into the future. As stated earlier, standards-conforming applications offer you peace of mind and no surprises.

Example Files:
Aquo_Bottle_RGB-a1
Aquo_Bottle_RGB-x3

Additional Links:
http://www.pdfa.org/
http://www.aiim.org/standards/