PDF Encryption and Security: Adobe PDF Encryption and Security History

Early PDF document security relied on weak 40 bit encryption and soon after it was released methods of breaking it were freely available on the Internet. In May 2001 128 bit encryption became available to prevent simple hacking of the native mode controls, and degraded printing, was also added. This did not mean that the hacking/cracking industry had not grown up to break the security measures that were in place.