I’m using Genius Scan+ and bought the cloud backup option for like $3 one-off, that enables automated exports to dropbox, google drive and a bunch of other services. Every document I receive is scanned and adequately named right away, and then automatically exported to both google drive and dropbox.

The dropbox client then again runs on my laptop and desktop and automatically syncs new files to the local folders, so I have the original scan on my phone plus two cloud backups and the local copies of the cloud backups on another two devices.

The original documents are kept in physical folders, neatly stored at home.