The first question to consider when creating a secured PDF file is how easy is it for others to remove the security?
The most popular method for creating secured PDF files was and still is password protection, but passwords are easily removed using any of the pdf password recovery programs – see PDF Encryption & Security. However, if you want to create secured PDF files then passwords are not the way forwards.
Adobe content server used PKI technology (see Public Key Infrastructure for a description), to get away from passwords, but, that meant the publisher needed the customer’s/user’s public key in order to create a unique secured PDF file. This is because using PKI, a secured PDF file had to be protected independently for each individual recipient, so the same PDF file would end up being secured hundreds or thousands of times depending on how many recipients there were. Clearly this was not a readily scalable architecture if your business suddenly went global.
Locklizard DRM secured PDF files are protected once only using long and random encryption keys. Decryption keys required to open authorised secured PDF files, and do not travel with the secured pdfs but are transparently relayed securely to the user’s computer and stored encrypted in a keystore. There are no passwords for the users to enter so there are none to give away, and users don’t have to send their public key to anyone (or even begin to understand that system).