Troubleshoot: "No Differences Found" Compare two PDFs

...when one or both PDFs are scanned. I'm trying to compare two contracts to see what has changed from the earlier version to the newer version.

Sometimes running a Compare Documents with a scanned document works; this time it says no differences found when the documents are clearly different. I've tried different permutations of settings - selecting and not selecting Scanned Documents for example. I've also run a Find on the scanned document so that OCR is run on each page then saved that version for the Compare.

Sometimes an unscanned version of the document is not available, so I need a resolution for this.

Any guidance would be appreciated. It seems like this should work after OCR.

Thanks,

Janis