Hello,
As you know, some PDF files are actually not encoded in an open standard and can only be open with Adobe's.
Today, I found a new kind of these at http://cyber.law.harvard.edu/people/tfisher/IP/IP%20Maps.htm (Try the links at the top)
I find these very problematic. Seriously, I don't understand why they even use PDF for what seems to be mindmapping / outlining documents. (How would these interactive documents render on paper anyway?) Anyway, I thought you might want to know about them.
Best, Hugo