Files went missing

After I downloaded the iCloud backup from my old iPhone to the new, all my files saved over the years disappeared from my Acrobat app (free). I don't have such an issue in my past phone upgrades so I sought help from Apple and the helpful staff couldn't find anything on iCloud. She told me the missing files could be on this site's cloud sunce I use the Acrobat app to download and open my files. Also she guided me to delete and reinstall Acrobat but still no files found. Please help.