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Protect a PDF with a password

Add a password to a PDF with AES-256 encryption and restrict printing, copying or editing. Free, and the file never leaves your device.

  • Free
  • No sign-up
  • No file uploaded
  • Windows, Mac, Android, iPhone

Your files stay on your device: nothing is uploaded.

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About this tool

Before sending a payslip, a statement or a contract, protect it with a password: without it, the PDF can't be opened. AES-256 encryption happens on your device.

When to use it

Send a confidential document

Protect the PDF, then share the password through another channel (text, call) than the file.

Archive personal papers

Keep your documents in the cloud without anyone being able to read them if they get into the folder.

Limit how a document is used

Prevent printing or copying text in PDF readers that respect these restrictions.

How to use

  1. Choose your PDF.
  2. Type the password twice and choose what readers may do.
  3. Click “Protect the PDF” and download it.

How it works

The PDF is encrypted by qpdf, a reference open-source tool compiled for the browser (about 430 KB, loaded only when you start the protection). Content is encrypted with AES-256 using your password.

When you restrict printing, copying or editing, a second random password is created to lock them: nobody knows it, so these restrictions can only be lifted from the original file.

Tips for best results

  • Use at least 12 characters, mixing words and numbers.
  • Don't put the password in the same email as the file.
  • Keep an unprotected copy of the document somewhere safe.
  • To change the password, unlock the PDF and protect it again.

Common problems and fixes

The PDF is already protected

Unlock it first with its current password, then protect it with the new one.

The recipient can't open it

Check they use a recent reader: very old software can't read AES-256.

The button stays greyed out

The password must have at least 4 characters and match in both fields.

Frequently asked questions

What encryption is used?

AES-256, the strongest level in the PDF standard, readable by all recent readers (Acrobat, browsers, phone previews).

What if I forget the password?

The PDF can no longer be opened: neither ZanaKit nor anyone else can recover the password. Keep an unprotected copy or write it down.

Is my password sent anywhere?

No. Encryption happens in your browser with qpdf; the password and the file are never sent or stored.

Are printing and copying restrictions reliable?

Most readers respect them, but some software ignores them. Only the opening password truly protects the content.

Related searches

Still stuck?

Ask on the forum: the category, the tool, your device sheet and the test result will be filled in for you.