When you are scanning paper documents to use on a DMS platform, a good way to add metadata is using a cover page.
For one of our clients, we introduced a client portal, where they would use a dossier management system on SharePoint to add information about different clients.
To add the client number on the cover sheet, one of the team workers came up with a really good solution: instead of writing the number down (and have a lot of misplaced documents due to failed recognition) we used a likert scale to add the digits.
This is a really easy to use system: every column is a digit, and you just have to mark the right number. The client number always has 5 digits, and marking them is a matter of seconds.
The result is a very low output due to failed recognition!