A scanned document becomes searchable when the text layer is added. That changes a photo archive into something you can query by keyword.
The practical use: scan a contract, search it by clause, scan a manual, find the page by term. On-device processing keeps the original and the text layer together on your phone.
Private Text Scanner is an Android scanner app I built for this. It performs text recognition on the device and can create searchable PDFs without an account. The free tier includes a usage allowance and rewarded ads; a one-time lifetime purchase unlocks the full version, with no subscription.
Searchable beats sortable for documents you cannot reorganize.
Disclosure: I am the developer of Private Text Scanner.
Private Text Scanner on Google Play
Disclosure: I am the developer of Private Text Scanner. This is a workflow note from Lexiang Technology, not professional advice.