Removing a PDF password is easy if you know the password. Enter the password, the tool decrypts the file in memory, and outputs an unprotected PDF. This is not a password-cracker — it can't bypass unknown passwords. If you've forgotten the password and don't have another way to recover it, no legitimate tool can help; contact the original creator.
Legitimate use cases
PDFs you generated with a password and later want to archive without it. Company documents where the password is known but adding it to a script is inconvenient. Sharing with someone who won't be able to enter passwords (e.g., in an automated workflow).
What this tool is not
Not a cracker. If you don't know the password, this tool can't help. There are commercial services that brute-force weak passwords, but that's a different product — and using them on documents you don't own is illegal in most jurisdictions.
Owner-password-only PDFs
Some PDFs have only an owner password (they open without a passphrase but block printing/copying). This tool removes those restrictions when the owner password is provided. If you don't know the owner password but can open the PDF, some viewers let you print-to-PDF which effectively strips restrictions.