Help > Authoring > Dialog Boxes > Edit Window > Tools Dialog Boxes > Compare Last Saved
  
Compare Last Saved
You can compare the currently active version of a document with the last saved version of the same document. After you select Compare > Last Saved, the Compare window displays changes marked according to the Compare Preferences settings.
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While the Compare command will detect the addition or deletion of graphics and equations, it will not detect changes within a graphic or an equation.