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How to password-protect a PDF

Checked against our tools on 12 October 2026

Open Protect PDF, add the file, choose a password and download the encrypted copy. Anyone who opens it has to enter the password first. The file is encrypted with AES-256 in your browser, so neither the document nor the password leaves your device. Then send the password some other way than the file.

Go straight to the tool: Protect PDF, Unlock PDF

The steps

  1. Open Protect PDF and add your PDF.
  2. Type a password and type it again to confirm. It must be at least 6 characters, but read the next section before settling on 6.
  3. Download the protected copy. Your original stays as it was.

How long should the password be?

The encryption isn't the weak point; the password is. Once someone has the file, they can run password-guessing software against it on their own computer, as fast as their hardware allows. Nothing locks them out after ten wrong tries. So:

  • Short passwords and single dictionary words can be guessed. Avoid "invoice1", a name, or a date of birth.
  • Use a passphrase of four or more random words, such as copper-lantern-mild-orbit. It's long enough to resist guessing and easy to read out over the phone.
  • Don't reuse a password from your email or bank.

How to send the password

Sending the PDF and its password in the same email undoes the point. Anyone who gets into that email, or receives it by mistake, has both. Send the file by email and the password by text message or a phone call, or agree on a password in advance.

What protection does and doesn't do

A password stops people who don't have it from opening the file. It doesn't stop anyone who does have it from saving, forwarding or printing it. Once you've shared the password, treat the contents as shared.

You may also come across "permissions" in PDF settings: options that block printing or copying while letting anyone open the file. They're enforced by the reader software, not by the encryption, and many viewers ignore them. Don't rely on them to protect anything sensitive. Protect PDF doesn't set them, so whoever has the password can print and copy as normal.

Free alternatives already on your computer

Microsoft Word on Windows: if the document starts life in Word, choose File, Save As, pick PDF as the type, select Options and tick "Encrypt the document with a password".

Preview on a Mac: open the PDF, choose File, Export, then set a password under Permissions. Older versions of macOS show an Encrypt checkbox instead.

Both work well. Protect PDF is useful when you have a PDF rather than a Word file, when you're on a phone, or when you're on a shared or work computer where you can't install anything.

If you forget the password

Neither we nor anyone else can recover it. That's the whole point of the encryption. Keep an unprotected original somewhere safe, or store the password in a password manager. If you need the password removed later and still know it, Unlock PDF does that, and our guide on removing a password from a PDF covers the details.

Common questions

Is Protect PDF free? Yes, for files up to 25 MB and 150 pages without an account. A free account raises that to 50 MB and 400 pages.

Will the recipient need special software? No. Every common PDF reader asks for the password and opens the file: Adobe Acrobat Reader, Chrome, Edge, Safari, Preview, and the built-in viewers on iPhone and Android.

Is AES-256 good enough? Yes. It's the strongest encryption the PDF format offers. With a long password, the file can't realistically be opened without it.

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