I would like your knowledge and advice in regards to PDF stamping or encryption using PHP. I have found a couple of API for achieving this but would like some sound advice. I have two PDF books as part of a membership program which I would like to protect as much as possible from theft. I have looked at many solutions on the net for protecting PDF ebooks etc and have tried out many of them. From a users perspective if i had to deal with the complexity of these solutions I would never buy anything again from that company. The best solution seems to be stamping with PHP, as i run a membership site that is selling a product and service I am planning on stamping the name and address and email of the person for added protection, which does not put the user out. I am also wondering that if instead encrypting using PHP and making the encryption password there email will be a better way to prevent over load for my server as I understand that this process is quite processor intense. I would be grateful for some advice regarding this please. What others have used? What you feel is the better solution. What is the best and easiest way to implement this?
Also may I ask when you get the PDF stamped or encrypted is it best to store that copy on the server so that if the user needs to download it again the server does not have to make another copy or is there a better way. I will be restricting my user to a max of 3 downloads to save on bandwidth.
Many thanks as always for your help.