A little background: my company updated all our PCs to Reader 9 while failing to inform our creative department, which is still using Acrobat Pro 8 on the MAC.
So here's the issue: Creative uses a PDF workflow for proofing print jobs. We save out the PDFs with commenting enabled for Reader 9 users. At random, the Reader 9 users' PDFs would get an error message when they open the PDFs stating that some of the usage rights have been deleted. This basically strips out the commenting rights. Another issue was that the PDFs wouldn't allow comment saves, so we'd have to export an FDF, resave the PDF, then import the FDF back in. Lastly, software crashes when Reader users try to save their comments.
After this fiasco, I installed Acrobat Pro 9 and this seemed to remedy the issues. However, we're still waiting on licensing for the rest of the Creative team which is still using Acrobat Pro 8.
Any clues as to what is going on? We still need to figure out compatibility issues between Acrobat 8 and Reader 9 until we get new licenses.