Save an unlocked copy of a PDF you already have the password for — no extra software needed.
You can only remove a password you already know — this is for unlocking your own files, not bypassing protection on someone else's. Open the file and type the password when prompted.
In Preview, go to File > Export, expand the options, and make sure "Encrypt" is unchecked. Save it under a new name. The exported copy opens without a password.
Open the unlocked PDF in your browser or reader, choose Print, and pick "Microsoft Print to PDF" (or "Save as PDF") as the printer. The new file has no password.
Store the password-protected original somewhere secure, and only share the unlocked copy with people who are meant to see it.