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Lock PDF – Add a Password to a PDF with AES-256 Encryption

Protect a PDF with a password using strong AES-256 encryption. Choose what others may do after opening it, such as printing or copying text.

  • 100% Free
  • No Signup
  • Quick Results

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How to use Lock PDF

  1. Choose your PDF file.
  2. Type a password twice, or click Suggest strong.
  3. Untick any actions you want to block, such as printing or copying.
  4. Click Lock PDF, download the file and test the password.

Why use our Lock PDF

The file is encrypted inside your browser. Neither the file nor the password is ever sent to us, so we cannot read or recover it.

  • AES-256 encryption.
  • Password strength meter and strong password suggestions.
  • Control printing, copying, editing, comments, forms and page changes.
  • Optional separate owner password.
  • Works on phones and computers.

Tips for the best result

  • Store the password in a password manager. It cannot be recovered.
  • Test the locked file before deleting the original.
  • Share the password through a different channel than the file.
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Frequently Asked Questions

How strong is the protection?

AES-256 is the strongest standard in PDF. A long, random password is what makes it hard to break.

Can you recover a lost password?

No. We never receive your password, so nobody can recover it for you.

Do the permission limits always work?

Major readers such as Acrobat, Chrome, Edge and Preview respect them. Only the password itself is a real lock.

Will old PDF readers open the file?

Any reader from the last several years does. Very old programs may not support AES-256.

Is it free to use?

Yes. This tool is free, has no daily limit and does not ask you to sign up or install anything.

Are my files uploaded to a server?

No. The work is done inside your own browser, so your file stays on your device. We never see or store your documents.

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