I think Gill mentioned something that I wasn't aware of and maybe others were in the dark, too, so I thought I would mention there is a function within Revisions that acts as a Track Changes. If you select your document, then go to the dropdown box for "More actions" and then select "Revisions."  From there, you can select different revisions and then click on "Compare Checked." When the page loads, it shows everyone's names in the upper right corner with different highlighted colors. As you review the document, you will see the different highlights for the different contributor's edits. Hope that helps!