F8 Toggles Synchronize Views
Synchronize Views 
allows you to pan and zoom the splits in unison. This is useful for comparing two different PDF files. You only have to pan, zoom or change pages within one of the splits and the other split will automatically perform the same function.
Syncing the views can be enabled by clicking Settings 
> Synchronize Views or by clicking the Sync button in the Status Bar at the very bottom of the Revu window. The Sync button in the Status Bar will highlight blue when Sync is enabled. If the Status Bar isn’t displayed on your screen, press F8.
