Unlock PDF
Remove password protection from a PDF on your device. Enter the opening password if required and download an unencrypted copy.
- passwords
- free
- no sign-up
- on device
- passwords
Password protect PDF
Password protect a PDF with AES-256 in your browser — free, with no sign-up, and your document and password never leave your device. Choose your PDF and a password, or generate a strong one; save the password safely, then download the encrypted copy.
Use only PDFs you own or are authorised to modify. This adds an opening password, not printing restrictions or content sanitisation.
How it works
- Choose your PDFSelect one unencrypted PDF up to 50 MB. It is checked locally; keep the original, especially if it is signed.
- Set and save the passwordEnter matching passwords or generate a strong one. Save it securely and confirm saving a generated password before you continue.
- Protect and downloadSelect Protect PDF. Download the copy after the encryption and opening-password checks finish. Send its password separately.
Questions
How do I password protect a PDF online for free?
Choose one unencrypted PDF up to 50 MB, enter and repeat a password or generate one here, then select Protect PDF and download the checked copy. Save a generated password before starting: both fields are cleared when encryption begins. The original is unchanged; no account or Acrobat installation is needed.
Can I generate a strong PDF password?
Yes. Generate a random 20-character password with the browser's cryptographic random number generator. Both fields are filled; you can show and copy the value. Confirm that you saved it securely before encryption. Replacing an entered password needs your explicit confirmation. Password settings opens the full generator in a new tab without passing your file or password.
Can I protect a PDF on Mac or Windows without Adobe Acrobat?
You do not need Acrobat or a desktop editor. This tool encrypts PDF files in a modern browser with JavaScript, WebAssembly, Web Workers and Web Crypto support. Download the copy and check it in an up-to-date PDF reader that supports AES-256. Large or complex files may exceed your device's memory even below 50 MB.
Is my document uploaded?
No. Your PDF and password never leave your device unless you choose to share the result. Processing runs in a disposable local worker, without saving the PDF or password in browser storage by the tool. The page loads its own engine files and may send anonymous usage events without document details.
Does a PDF password prevent printing, copying or editing?
This tool encrypts a new PDF with AES-256 and requires your password to open it. After opening, printing, copying and editing are allowed. Permissions passwords and viewer restrictions are a different mechanism; this is not a permissions editor or DRM. Use a long, unique opening password and send it separately from the PDF.
Can I change an existing PDF password?
First use Unlock PDF with the current opening password, then protect the unencrypted copy here. Already-encrypted files, including printing-only restrictions, are not rewritten by this tool. Unknown passwords cannot be recovered.
What happens to digital signatures?
Adding encryption rewrites the PDF and can invalidate signatures or certification. Detected signature fields or certification markers require an extra acknowledgement. Keep the signed original: this tool does not verify signatures or guarantee a signature-preserving copy.
Are text, forms and links kept?
Pages are not printed, rasterized or flattened. Before download, the tool verifies AES-256 encryption, that the new password opens the result, that an empty password does not, and that the page count matches. Review important text, form values, links and attachments yourself. Active content may remain: this is not a sanitizer.
What are the limits and password rules?
One PDF up to 50 MB (50,000,000 bytes). Passwords must match exactly and fit within 127 UTF-8 bytes; spaces are not trimmed. Empty, whitespace-only, null or invalid Unicode passwords are rejected. Complex files can fail below the size limit. Use a modern PDF reader and keep your password: there is no recovery service.
Do I need an account?
No. You can use this tool without an account.
Related tools
Password Generator
Create a random password with the length and characters you need.
- passwords
- random
- generator