What is a good strategy for obtaining comments on a LaTeX document from non-LaTeX using collaborators?

Get them to print the document and mark on it, then fax it to you. (If they have a fast scanner, they could scan and email, instead of faxing.)

Then, collect all of the marked-up documents and make the first-author decisions as to what to change. (Yes, there will be conflicts in the suggestions.)

Alternatively, turn on line numbering and get them to send you plain-text emails with comments tied to lines.

These methods work. Twiddling with PDF comments may be of use in text-only material, but scientific work normally is awash in symbols and diagrams, and suggesting changes to these is very hard in text-only form.

http://www.crocodoc.com

The site is completely free. You can upload any document or PDF to the site, share the link with people, and everyone can comment online using the commenting tools the site offers.

The best of it is that each person can reply to comments. You can highlight text, strike it out, draw and comment.

I used this for my master dissertation, I had three supervisors, one with Windows, one with Linux and one with Mac. This worked great as no one needs to install anything.

If you have Acrobat Professional then you can use it to activate your document so that collaborators can comment using Adobe Reader. As far as I know this lets them use the same commenting tools that Acrobat Pro has, for what that is worth (maybe ok for small edits, not so good for major rewriting).

Its in the menu at: Advanced -> Extend features in Adobe Reader...