A document management system for the home?

Question

Document flow

Good afternoon,
please advise a simple DMS system for the home.
My grandfather keeps all the records, checks, documents, letters, contracts, etc. from the 30s.
He worked as a court.med. expert, investigator, doctor and lawyer. And now a pensioner with a craving for poetry, photography, filmmaking and electronics, soldering his dimes and quadcopters. With photos and videos everything is clear. But everything else is not very good.
Almost all of his old records are digitized and stored in .jpg, pdf. New in .txt and .doc.
It saves all files just like that on disks. So it's hard to find the files. Files txt, doc, pdf, dicom .... ~ 500.000
Search is a system in which all this can be uploaded, tagged, searched both by files and by content, and saved letters with attachments. And quickly scan new documents and save / attach to projects.
We need a system that is not tied to the clouds and can work on the grandfather's home server.
THX

Answer 1

If the file names are adequate, then the small tool Everything will help a lot.

Answer 2

I'll raise a question.
Did you find anything? I tried several free ones, but it's not the same.
Now I'm testing LogicalDoc, not very well yet. I also tried feng office. But they are monsters.
The closest is Paperless (Mariner Software), but you have to do the categories by hand. There is hosted, but I don't want to pay 5€/month for my files :)