I've been Googling all afternoon and I'm about ready to raise the white flag.

I'm looking for a web app that uses my Dropbox credentials/has access to my .pdf files on Dropbox. I'd like to annotate these .pdf files in a web browser. I'd like for this file to be saved back into Dropbox, so that I can view these files across my devices/computers when I'm not at work.

The closest thing I've found to something this is GroupDocs, but tldr; it refuses to save back into Dropbox. I've attempted to contact their support but their user registration email for support (which is separate from the product credential) has yet to hit my inbox three hours after registering. Trying to register on their forums takes me back to my file dashboard (wtf?)...I'd like to give this group/developer the benefit of the doubt, but my experience has been a frustrating one thus far.

Surely there has to be someone out there who's meeting this consumer interest? I can't be the only person interested in this type of workflow/functionality.