How to password protect a PDF

To password protect a PDF, open it in a protect tool, type a strong password, and save the encrypted copy. Anyone who opens the new file must enter the password before they see a single page. Send the password by a different route from the file, so one intercepted message is not enough.

What password protection actually does

When you protect a PDF with an open password, the file's contents are encrypted. Encryption scrambles the data so it is unreadable without the right key, and the password unlocks that key. Without the password, PDF readers show nothing but a password prompt.

There are two kinds of PDF password, and it helps to know the difference:

An open password (sometimes called a user password) is needed to view the document at all.
A permissions password (sometimes called an owner password) controls what people can do after opening, such as printing, copying or editing.

If your goal is privacy, you want an open password. Permission restrictions on their own are easy to get around with many tools and should not be relied on to keep anything secret.

When to password protect a PDF

payslips, tax documents and bank statements you email to an accountant;
copies of your ID or passport sent to a landlord or employer;
medical letters and test results;
contracts and offer letters before they are public;
client files you store on a shared device or cloud drive.

How to password protect a PDF on your phone

Open the PDF in a password-protect tool.
Type a strong password. Use a long passphrase rather than a short word.
Type it again to confirm.
Save the protected copy with a clear name.
Open the new file to check it asks for the password.
Store the password somewhere safe, such as a password manager.

Keep or delete the unprotected original depending on where it is stored. If it is on a shared device, delete it once you have the protected copy.

How to choose a good PDF password

The strength of a protected PDF depends mostly on the password. A short or common password can be guessed by software that tries huge numbers of options quickly.

Make it long. Several random words, such as "lantern river paper seven", are easier to remember and harder to guess than a short jumble.
Avoid personal details. Birthdays, phone numbers and pet names are the first things an attacker tries.
Use a new password for each sensitive file if you send them to different people.
Never reuse your email or banking password.

PDF encryption comes in different strengths. Older schemes, such as RC4, are weaker than modern AES encryption. For everyday privacy a long, unique password matters most. For highly sensitive documents, also think about how you send the file, not just how it is locked.

The most common mistake is sending the password in the same email as the file. If that email is forwarded or the account is compromised, the protection is worthless.

Better options:

tell the person the password in a phone call;
send it by a different app from the file, such as a text message if the file went by email;
agree a password in person in advance for regular exchanges.

Remember: you cannot get it back

PDF passwords cannot be recovered or reset like an online account. If you forget the open password, the file is effectively locked for good. Always keep the password somewhere safe before you delete the original. If you later want to remove the password from a file you own, see how to remove a password from a PDF.

Protection is not the same as redaction

A password keeps people out of the whole file. It does not hide parts of it from people who do have the password. If you need to share a document but keep some details private, remove that information properly first. The guide to redacting a PDF explains how. And if you are sending several protected files, bundling them can make things tidier. See how to send several PDFs as one ZIP file.

Password protecting PDFs with PDF Burrow

PDF Burrow has a Password Protect tool that encrypts your PDF so only people with the password can open it. The encryption happens on your phone, so the document is not uploaded anywhere. If you need to hide specific details as well, Redact PDF permanently blacks out sensitive text or areas before you lock the file. For more on why on-device processing matters, read are online PDF tools safe.

Frequently asked questions

Can I password protect a PDF without an app?

Some computer programs and print-to-PDF options can add a password. On a phone, you usually need a PDF app with a protect tool.

Does a password stop someone printing the PDF?

An open password stops anyone without it from opening the file at all. Once someone has the password and opens it, permission settings may limit printing, but those limits are easy to bypass.

Will the recipient need a special app to open it?

No. Password-protected PDFs open in normal PDF readers, which ask for the password first.

What happens if I forget the password?

There is no reset option. Keep the password in a safe place, such as a password manager, before you delete the unprotected original.