There are two kinds of PDF password. An open password is the one you type to view the file at all. A permissions password leaves the file readable but blocks printing, copying or editing. If you know the password and just want to stop being asked every time, you can remove it — that's what the Unlock tool does.
How to do it
Open the Unlock tool, drop the PDF, and enter the password you already use to open it. The tool returns a copy with the encryption removed, so it opens straight away from then on.
An important limit
You must know the password. We do not crack, guess, or brute-force PDF passwords — that would be a tool for opening other people's files, and we won't build it. Unlock only removes protection from a document you can already open. If you've genuinely lost your own password, there's no shortcut here.