I send them the docs with a title like: Chapter 1.doc
What I ask them to do is save it with their intials: Chapter 1XYZ.doc
To get around that issue, I set up individual editor accounts for them to post their individual edits, while I provide a separate "Latest Copy" folder of all the final changes (in case they want to review the final version of the story, as each edit may change things).
Dropbox and "Review Changes" is powerful, but generally, editors are like authors, they do their best work during their first pass. Each time they review a work, they tend to miss more items. The same is true of authors, the longer they review any given chapter, the more typos they'll miss, because they anticipate what will appear next.
Thus the best approach is to ONLY send your editors the final version of a chapter, incorporate any changes you agree with, and report any changes you DO make (so they can object if you didn't address their particular issue). Typo corrections can usually be made without saying "Change hte to 'the'".
The key is, editors are only interested in the final copy, not in what went before, research material, back story, graphics or inspirations. They're responding to the words on the page, and other info. is immaterial, as it won't affect what readers experience.
That said, if I made substantive changes to the story, i'll run the changes by my editors, so they can catch any new typos I introduced with the changes, as well as opine whether the changes benefit or hurt the story.