Duplex scanners only - After Acrobat DC July 2015 update, selecting the Sides > Both Sides option in the Custom Scan as well as Presets (Autodetect Color Mode, Black and White etc.) result in only the Front Side being scanned.
We'll be able to fix the issue in the next update of Acrobat DC. The workaround is to use the Scanner’s Native Interface through Custom Scan. Follow the steps below.