Just recently I had to look at, and print a few pages from, a PDF document. Knowing where it came from, a corporation that is only very slowly dipping a toe in the water of software other than the big names, I'm sure it was done with Adobe.
Now I don't even have the Adobe Acrobat reader on my system, when I try to install it, the install crashes. But Fedora comes with several other PDF readers, and the default is set to "Evince" which works fine MOST of the time.
But I got this PDF, and one page was a picture of a tax form, and when I tried to print it, the tax form came out as a big black blob - man, does that waste ink! Obviously I killed the print job to try something else. (Just VIEWING this tax form was fine, only printing messed up.)
I remembered using "Xpdf" a while ago, so I tried that, and voila, the tax form printed perfectly. Since I knew there were more tax forms in there, I used Xpdf for the rest of the job.
So here is a case where two different PDF viewers reacted differently to the same PDF file. I think what we need is is an OPEN DEFINITION for PDF files, probably a subset of Adobe's definition, that any OSS viewer can follow and get the proper results - and ask the user what to do with files that don't follow it.
And tell Adobe they can either follow the open definition, or stuff it where the sun don't shine!