Yesterday I was doing some experiments with Adobe Illustrator. According to some web sites, The CS5 version saves its files as PDF, though with the extension .AI. When you save a file, though, the options dialog has a checkbox labeled “Create PDF Compatible File.” I unchecked it and saved the file, then opened it in JHOVE. JHOVE says it’s perfectly good PDF — indeed, PDF/A. Then I tried opening it in Preview, and this is what it looked like:
If you don’t actually look at the file but trust the mere fact that it’s a PDF, you might put it into a repository and find out later on that it’s worthless as a PDF. What’s happening is that PDF can embed any kind of content, and this one embeds its native PGF data. Any PDF reader can open the file, but only an application that understands PGF can use its actual content. Anyone putting PDF into a repository should be aware of this risk.
It’s outside the scope of JHOVE to check whether embedded content is acceptable to PDF/A, so the claim that it’s correct PDF/A is probably spurious. It is, however, definitely legal PDF.
This type of situation helps to show why PDF/A-3 is a bad idea.