If you really want to protect your scans, then upload them to your own password protected forums or blog. If you upload to a public platform like MD, then you'll have to accept that there are low lives out there who will exploit your work. It's a trade off between getting lots of people to see your release vs not being ripped easily by ad-gregators.
For the record, if there was a straightforward way to prevent ripping while not impacting real users, we would be doing it. And we would have sold such a system to Amazon and be millionaires.