Elcomsoft's Advanced PDF Password Recovery Professional works.
It's also recommended here: http://labnol.blogspot.com/2007/01/how-to-open-password-protected-pdf.html
It took it less than a second to find a three letter password, all in lowercase. Granted, most PDF passwords would probably be a bit more than that, but this one was for homework solutions, and I was asked to crack it for someone.
So yay Elcomsoft.