Key Challenge: Licensing

One of the key challenges all ebook distributors face is the ability to lock a file (with a password or something) to prevent people from passing on the ebook or even reselling it, or taking its content, after purchase.

The solution is to lock down the file in a way that still preserves enough rights for this to be acceptable to the user. One way to do this is to assign a key or password each time the file is distributed, but that's a horrible amount of work for a human being.

There are some proprietary solutions out there to do this, and here's the request - is there a way to use Drupal to process the PDF for export in such a way as to assign a user-configurable password to the file... all without the author having to touch it each time?