UtilTools

Password Protect PDF

Encrypt a PDF with a password, locally.

Password Protect PDF encrypts your document with AES-256 using the standard PDF security handler, so any compliant reader will ask for the password before opening it. Encryption keys are derived in your browser with the Web Crypto API and the file is written locally — the password is never transmitted anywhere.

Loading Password Protect PDF…

Runs entirely on your device. No file or text you enter here is uploaded. How to verify it.

How to use Password Protect PDF

  1. Open the PDF you want to protect.
  2. Set an open password, and optionally an owner password and permissions.
  3. Encrypt and download the protected file.

Questions about Password Protect PDF

Which encryption is used?
AES-256 under PDF 2.0 revision 6 — the strongest option the PDF specification defines. Keys come from crypto.getRandomValues() and are derived using the SHA-256 based algorithm from ISO 32000-2.
What happens if I forget the password?
The file is unrecoverable. There is no backdoor, no recovery key and no reset — that is what encryption means. Write the password down somewhere safe before you close the tab.
What is the difference between the user and owner password?
The user password is required to open the document. The owner password only lifts the permission restrictions (printing, copying, editing). A file with an owner password but no user password opens for anyone, and the restrictions rely on the reader honouring them.
Are permission restrictions real security?
No. Restrictions on printing or copying are flags a compliant reader chooses to obey. Only the open password provides actual cryptographic protection. The page says this plainly because too many tools do not.
Will the encrypted file open on a phone or in an old reader?
Current Acrobat and Reader, Apple Preview and Books, Chrome and Edge all handle AES-256 revision 6, so phones are fine. Readers predating roughly 2017 may not understand it and will refuse the file outright. Only revision 6 is written here, so there is no weaker fallback to pick.
How strong does the password need to be?
The encryption is only as good as the password, since that is the sole input to the key. A short or common one can be guessed offline at high speed by anyone holding the file. Use a long passphrase of several unrelated words, and send it to the recipient by a different channel from the document itself.
Is Password Protect PDF really free, with no limits?
Yes. There is no account, no daily cap, no file-size tier and no watermark, because there is no server cost to recover. The site is funded by clearly disclosed partner recommendations on the Partners page, never by metering the tools.
Are my files or text uploaded when I use Password Protect PDF?
No. Everything is processed by JavaScript running in your browser, on your device. You can verify it: open your browser's developer tools, switch to the Network tab, and use the tool. You will see no request carrying your data — because there is nowhere for it to go.