Quoting from Word 2002 Help, which you can access in Word by pressing
the F1 key on your keyboard or by clicking on Help on the menu bar at
the top of your Word window:
Compare and merge documents
1. Open the edited copy of the document.
2. On the Tools menu, click Compare and Merge Documents.
3. Select the original document, click the arrow next to Merge, and then
do one of the following:
• To display the results of the comparison in the original document,
click Merge.
• To display the results in the currently open document, click Merge
into current document.
• To display the results in a new document, click Merge into new
document.
Notes
• To ensure the best possible merge results, make sure that the
Store random number to improve merge accuracy check box is selected on
the Security tab of the Options dialog box (click Options on the Tools
menu).
• If you've used the Versions command on the File menu to save
multiple versions of the document in one file, and you want to compare
the current version with an earlier one, you must first save the earlier
version as a separate file under a different name.