I am TRYING to collaborate on a PDF with a colleague, so I shared it with him utilising Acrobat's "Share this file with others" link, after I had added check marks and comments to sections of it. After coming back to it (he hasn't even opened it yet) I can't edit the document anymore and it's infuriating as I've essentially lost all of the work I've done thus far. PLEASE FIX this glaring bug!!