Can I open a locked PDF without the owner's password on MacBook?

A pdf document has been locked. I have no idea how or why. Now, Im trying to open it and I need to enter the 'owners' password. I have tried the password/pin I use to log on. It doesn't work. If I set a password when I got my Mac, then I have forgot. But I would have set a 'hint'. How do I find out the 'hint' I would have set?

[Re-Titled By Moderator]