When the current page contains two or more displayed layers that are relatively similar, you can find out what is the same and what is different about them.
Comparing layers
To compare layers:
1. Deactivate the active edit layer on the page, if any.
2. To do a layer comparison that ignores differences in color, activate View ® Monochrome.
All layers appear black and white. In the Layers window (Preference ® Layers):
3. Right mouse click the name of a layer (regardless, all displayed layers are compared).
4. From the menu that appears, choose Compare.
5. In the Layer Compare dialog box, click the compare option you want. For an explanation of each, click Layer Compare options.
The page display changes as you select each option.
6. When you are satisfied with the page display, click OK.
The page is displayed according to the Compare option you last selected.