I'm writting a ebook and I'm gonna to sell it soon.
I'd sell it at Google Play Store, but here in Brazil they don't accept PayPal as payment (and many brazilian don't have a credit card), so I think that the best option is to sell it by myself.
I could sell it also at Amazon, but the Kindle format just sucks when you work with (a lot of) equations.
But, of course, there's a problem about sending the pdf file to the buyer. My friend suggested me to lock it with a serial key - like a software. Then a person could open it just in one or three computers. I know there's a package that lock the pdf file with a password (that I create), but I'd like to have a way that block this password when it's used a lot of times - really like a software.
Is it possible?
Do you have any other ideas to protect a pdf file?
I'm gonna take the copyright of my ebook here in Brazil and I know that I can't protect it totally, but I'm trying to do everything I can do to protect it.
There's also a brazilian site (www.hotmart.com.br) where you can publish anything you want and they say that, about pdf files, they print in each page the document number of that one who bought my ebook.