Unlock only works if you know the password. That is the ethical and technical line. Unlock PDF feeds the password to pdf.js, decrypts in memory, and writes a copy without the restriction dictionary.
We will not add a brute-force option. If you forgot the owner password on your own file, the honest path is the original export, not a “cracker”.
After unlocking, you can Protect again with a new password, or leave it open for a printer that cannot prompt.
Files stay in the tab. A cloud unlocker that “requires the password” still receives the plaintext after you type it.