In 1993 I worked at the Australian Electoral Commission for a while. They had a similar requirement pertaining to paper, particularly the forms people fill in to enrol or re-enrol at their current address. (Showing up to vote is compulsory, so the AEC makes it really easy to enrol. There's even a "walks" team that just goes door to door getting people to fill in their enrolment form.) They scanned every paper form to magneto-optical cartridges (the most compact replaceable storage technology at the time) and kept the paper filed in boxes, never to be touched. Maybe once a week a paper form would need to be fished out of filing because it had escaped scanning.

That is: this was a completely solved problem twenty years ago.