This option compares the documents and displays only what changed between the two documents. The documents being compared are not changed. This type of comparison is always displayed in a new, third document.
If you want to compare changes from a number of reviewers, do not select this option. Use one of the merge commands instead.
If either version of the document has previous tracked changes, Microsoft Word displays a message box. Click Yes to compare the documents.
Microsoft Word displays a new, third document in which tracked changes in the baseline document are accepted and changes in the selected document are shown as tracked changes. The documents being compared are not changed.
Note 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.