Sorry to be harsh but it's true. Facebook disallows uploading of PDFs or document filetypes or animated GIFs for any sort of collaboration or group communication. There is absolutely no technological excuse for that. Twitter's limit needs to be upped to about 300 characters to say anything useful. 100% of their users agree. Unfortunately the higher ups can't seem to pull their heads out of their asses. Both FB and Twitter constantly try to stop users from linking to offsite content. How about allow it on your own website!!!
So now that's what they claim they're doing and yet I know they'll screw it up too badly to be useable. They'll stuff it full of ads, break 10 different countries' laws with it, Zuckerberg will say something offensive and blatant about it and piss off the board, and it will be inferior to even the garbage pile of a site design known as CNN.com. The real solution is to fire everyone who keeps making these horrible decisions about the way super massive sites are designed.