PDF Lock

Password protect your PDF files — free, private, no uploads

Click to upload or drag and drop a PDF file

Upload a PDF to add password protection

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Use our free PDF lock tool to password protect your PDF documents. Upload a PDF, set a password, and download an encrypted copy. All processing is client-side — your file and password never leave your device.

How to Lock a PDF Online Free

  1. Upload your PDF — Click the upload zone or drag and drop a PDF file.
  2. Set a password — Enter the password you want to use to protect the document.
  3. Lock — Click "Lock PDF" to encrypt the document with your password.
  4. Download — Save your password-protected PDF. No uploads, completely private.

Why Use Our PDF Lock Tool?

Most online PDF lockers require uploading your document to a server — a privacy risk for sensitive files. Our tool runs entirely in your browser using pdf-lib. No uploads, no file size limits, no watermarks, and no registration. Uses AES-128 encryption to secure your PDF. Works offline after the initial page load on Chrome, Firefox, Edge, and Safari.

Frequently Asked Questions

How does this PDF lock tool work?

Upload a PDF, enter a password, and click Lock. The tool uses pdf-lib to encrypt your PDF in your browser and creates a password-protected copy for download.

Is this PDF lock tool free and private?

Yes, completely free and 100% private. Your PDF and password are processed in your browser and never uploaded to any server.

Can I recover a lost PDF password?

No, pdf-lib does not support password recovery. Save your password somewhere safe. If you lose it, use our PDF Unlocker tool if you remember it later.