I understand that if I use pdf stamping and later I upload a new version of the pdf ebook, the buyer will have access to the new version (via the original "click here" link) but it won't be stamped. The only way to get it stamped is for the user to check the item out again. I think that is correct. My question is, is there anyway to get new versions of the pdf file stamped? Perhaps a buyer would receive a promotion code when they first purchase the ebook which they could then later on use to get a free update when a new version is released, would that work?