Depending.. these new PDFs have rules built into them.. they're very secure and based off a server at other companies.
Example: I have my own PDF server, you take a file.. the only way to crack it would be to have the information from my server, authorize, then get the rights to do. It's not an easy process.. and Adobe knows it and they're charging a hell of a lot for it.
I have never heard of someone being able to break these PDFs, since the info is built right into the file and not accessible unless authorizated against the issuing server.. same principle as certificates..
but yet, anything can be cracked..it's a matter of time.. but for the purpose of this thread, it's not going to happen.