Underpinning all document security systems is encryption. If your document security system does not use this, then forget it – it’s just smoke and mirrors. Encryption is the technology that hides documents from those who are not authorized and verifies that the content the originator created is unchanged.
If you are an authorized recipient of encrypted information, you can do anything you like with that information once you have removed the encryption. That is the Achilles’ heel. The recipient of documents that have been decrypted can go on to use them in any way they wish, and to alter them in any way they wish. That does not mean they can pretend that someone else created them, which is a valuable protection, provided you can be bothered to look closely at the authenticity of the documents you receive. But judging by the number of people taken in by fake messages from financial institutions or amazing offers from Nigeria, maybe looking to see if a document is real is not a top priority.
Encryption, therefore, is just the building block of document security and is of limited use after the document reaches its intended recipient.