Compare versions of a Word Document with Microsoft Word
You can easily compare two versions of a Word document using Microsoft Word in Mac OS X.
* Launch the two documents you want to compare within Microsoft Word
* Go to the Tools Menu
* Select Track Changes
* Select Compare Documents
* Select the two documents you want to compare
You’ll be shown a side by side comparison of the files and the changes will be highlighted and easy to spot. If you’re a writer, researcher, or editor, you’ll find this feature very useful! As far as I know this comparison tool is not included within Apple’s Pages application (at least not in version 3.0 that I have), hopefully in a newer version it will be a feature, it is too helpful to not be!
If you’re looking for a more developer orientated version of file comparison, check out FileMerge.

[...] 3) I keep running notes on which sections of the MS have been changed most so I can reread them. If you use Word on a Windows machine, you can skip this step AND section 4 and just compare versions in Word itself. [...]