Chesseburger
We also keep a paper trail for obsolete drawings and obsolete revisions.
Some yers ago, I've started an experiment: save these obsolete docs. on the server, to avoid paper. The result was the growing unusefull space ocupied by these files.
Maybe it depends on your work, but I think the probability of turning back on a design doesn't pay the price of obsolete files management. Just keep it in paper for history purposes.
I my opinion, the biggest goal in a PDM is not the revisions history, but to assure that the available drawing is actualy the latest approved revision, and that it can be revised only under certain safe conditions.
Regards