I've had a quick look around and 'stamping' seems like a good idea. Basically, when someone purchases your PDF their name and email address (and possibly home address) are stamped onto the PDF to discourage sharing.
I also saw book guard pro which will secure a pdf (PDF Security - BookGuard Pro - Protect Your PDF's, eBooks & More) but I'm thinking this outputs the file as a .exe which may put people off (or would it?). Would this also mean that they couldn't put it on a handheld device to take with them portably?
Are any of you guys securing your PDF ebooks? Do you recommend any methods? Pro's and Con's etc.
Thanks for any suggestions.