PDF Tools

Protect PDF

Add a real password and AES-256 encryption to a PDF — entirely in your browser. Set a password to open the file and choose what readers may do. Your PDF and password never leave your device.

Runs entirely in your browser — nothing you type is uploaded.

This tool runs in your browser. Please enable JavaScript to use it — the guide below explains what it does.

Note: the encryption runs in your browser with JavaScript. With JavaScript off you can read this guide, but the tool controls will not appear.

Password-protect a PDF with real encryption

This tool adds a genuine password and AES-256 encryption to your PDF, entirely in your browser. It uses a bundled cryptography library together with the browser's Web Crypto API to encrypt the file's contents — this is standard PDF encryption (ISO 32000-2), not a cosmetic flag or a renamed file. The protected PDF genuinely requires the password to open in any compliant reader. Your file and your password never leave your device.

How to use the Protect PDF tool

  1. Add your PDF — drag it onto the drop area or click to browse.
  2. Set a password to open the file, and confirm it. Use the show-password option to check it.
  3. Choose reader permissions — whether printing, copying text and editing are allowed.
  4. Click Protect PDF, then use Download protected PDF to save the encrypted file.

How it works

When you click Protect, the tool loads your PDF in memory and encrypts it with AES-256. The encryption key is derived from your password using secure random salts generated by the browser, and the permission choices you make are written into the encrypted document. To make the permissions meaningful, the tool sets a separate random owner key internally so compliant viewers enforce them for anyone who opens the file with your password. Your password is used only for this operation, held only in local variables, cleared afterwards, and never stored in the browser, logged, or sent anywhere.

Benefits and use cases

  • Share sensitive documents — contracts, statements or records that should need a password to open.
  • Real security — standard AES-256 encryption, verifiable in any PDF reader.
  • Control usage — limit printing, copying or editing for readers.
  • No account, no upload — confidential files never leave your computer.
  • Works offline — once the page has loaded, no connection is needed.

Limitations

Choose a strong, unique password — the protection is only as strong as the password you pick, and if you forget it the file cannot be recovered (there is no backdoor, and nothing is stored). PDF permissions such as "no printing" are honoured by compliant viewers but, like all PDF permissions, are advisory rather than an absolute technical guarantee. You cannot protect a PDF that is already encrypted; unlock it first. Very large PDFs use more memory while they are processed in the browser.

Privacy

Everything runs locally in your browser. Your PDF and your password are never uploaded, stored, logged or shared, and the tool makes no network requests.

Frequently Asked Questions

Is this real encryption or just a cosmetic lock?
It is real encryption. The tool applies standard PDF AES-256 encryption (ISO 32000-2) using a bundled cryptography library and the browser's Web Crypto API. The resulting file genuinely requires the password to open in any compliant PDF reader — it is not merely a renamed file or a metadata flag.
Is my PDF or password uploaded anywhere?
No. The PDF is encrypted entirely inside your own browser, and your password is used only in memory for that operation. Nothing is uploaded, and the password is never stored, logged, saved in your browser, or sent over the network.
What do the permission options do?
When you set an open password, you can also choose whether readers may print, copy text or modify the document. These permissions are written into the encrypted PDF and are enforced by compliant PDF viewers. As with all PDFs, permissions are advisory rather than an absolute guarantee, but standard readers honour them.
Which encryption is used, and is it strong?
The default is AES-256, the strongest standard PDF encryption. The encryption key is derived from your password with secure random salts generated by the browser, so a strong, unique password gives strong protection. Choose a long password you do not use elsewhere.
Can I protect an already-protected PDF?
Not directly. If a PDF is already password-protected, unlock it first (with the Unlock PDF tool and the current password), then protect it again with your new password. The tool will tell you if the file is already encrypted.

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