There two passwords you can apply to a PDF. The first is the owner password. Opening a PDF with this password will allow you full access to the PDF when a user password has been assigned as well. This means that even if printing was disabled you will still be able to print the PDF when using this password. No password will be prompted for when opening the PDF if you secure it with only an owner password. The second is the user password. Opening a PDF with this password will restrict you based on how the PDF was password protected (printing may be disabled, for instance).