3 Automatically marking document edits with Track Changes
If you want to be able to track what changes have been made to a document, then you want to use the Word feature called (big surprise here) Track Changes.
Here’s a little tutorial on how to turn on Track Changes in Word (both the menu-based versions 2002 and 2003 and the Ribbon versions 2007 and up), plus some notes about the feature’s little quirks you’ll want to watch out for.