I've published an ebook in Adobe Acrobat PDF format. I sell this ebook DRM free and take what I consider a friendlier/less obtrusive approach of using a service to "stamp" the customer's name and email address onto each page of the ebook as a way to discourage piracy.
I would like to take this same approach for selling the ebook in ePub and/or Kindle formats. Unfortunately, I haven't been able to find any stamping services for ePub or Kindle. Is DRM my only anti-piracy option when using ePub and Kindle?
For a reference point, ebookstamper.com stamps ebooks in PDF format. No, they don't do anything other than PDF.