Guide
How to password-protect a PDF (free, on Windows and Mac)
Lock a PDF so only people with the password can open it. Free methods for Mac, Windows and the browser — and how to choose a password that actually protects it.
Updated 4 October 2026 2 min read
Payslips, medical letters, signed contracts, bank details: some PDFs shouldn't be readable by whoever happens to see the email. Adding a password encrypts the file, so it can only be opened by someone who knows the password.
On a Mac: Preview
- Open the PDF in Preview and choose File → Export….
- Use the Encrypt option (called Permissions… on recent macOS versions) to require a password to open the document.
- Save the copy, then check it asks for the password when you open it.
On Windows
Windows can't encrypt an existing PDF on its own. If the document comes from Microsoft Word, choose File → Save As → PDF → Options and tick Encrypt the document with a password. For a PDF you received or scanned, you need another tool — Adobe Acrobat Pro does it, but it is paid.
In any browser, without uploading the file
Sending a confidential PDF to a website to have it encrypted somewhat defeats the purpose. A tool that runs in your browser encrypts the file on your own device with AES-256, the strongest standard PDF encryption, supported by Adobe Acrobat, Preview, Chrome and Edge.
Choosing a password that protects
- Length beats complexity: four random words (e.g. “lamp-orbit-cactus-ferry”) are stronger than “P@ss1!”.
- Never reuse your email or bank password.
- Send it separately from the file — by text message or phone.
- Keep it somewhere safe: a forgotten PDF password can't be recovered.
Need to remove the password later?
If you know the password, you can save an unlocked copy at any time.
Frequently asked questions
How should I send the password?
Through a different channel than the file — for example, email the PDF and send the password by text message or tell it over the phone.
Can a password-protected PDF be cracked?
A long, random password with modern AES-256 encryption is not realistically guessable. Short or common passwords can be found by trying millions of guesses, so length matters most.
What is the difference between an open password and permissions?
An open password encrypts the whole file: nothing can be read without it. Permissions only ask PDF readers not to allow printing, copying or editing — useful, but much weaker protection.