In need off version control for documents.

We've been using RDM for many years now. Great product. We use a secure SQL server for our database.
We mainly use it to keep the configuration data from our customers as well as starting rdp-connections from within and so on.
The problem we often have is that user A closes his laptop without closing all open documents. User B then opens and modifies one of these documents. A few days later user A makes modifications in the document that is still open on his laptop and thus overwrites the changes from user B when he saves the document.
This happened many times and we lost important data.
It would be great to have some sort of version control so we could revert to another version when someone has overwritten a file.