Sending a payslip, a medical letter or a signed agreement by email means it can sit in several inboxes for years. A password on the PDF adds a real layer of protection for very little effort.

Two kinds of PDF password

• Open (user) password: required to open the file at all. This is what most people mean by "password protected".
• Owner (permissions) password: controls what a person can do once the file is open, such as printing or copying. It is a polite lock rather than a strong one, because some software ignores those restrictions.

If the document is private, the open password is the one that matters.

How to add a password

1. Open Protect PDF and upload your file (up to 50 MB).
2. Enter the password you want people to type to open it.
3. Download the protected PDF.
4. Open the new file yourself and confirm the password works before sending it.

Keep the original unprotected copy somewhere safe. If you forget the password on the only copy, nobody, including us, can recover it.

Choosing a password that holds up

Length beats cleverness. A phrase of four or five unrelated words is easier to remember and much harder to guess than "P@ssw0rd1". Avoid names, birthdays and anything that appears on the document itself. Use a different password for each file that matters, and store them in a password manager.

Sharing the password safely

Never put the password in the same email as the file. Send it another way: a text message, a phone call, or a messaging app. If you can, agree it in advance, for example "the last four digits of your account plus the invoice number".

What a password does not do

A password protects the file in transit and at rest. It doesn't hide the fact that a document exists, and it doesn't stop an authorised recipient forwarding it. If parts of the content should never be seen by some readers, remove them instead: see how to redact a PDF safely. To brand a document as confidential, Add Watermark puts text across every page.

Removing a password later

If you own the file and know the password, Unlock PDF creates an unprotected copy. Our guide to unlocking PDFs explains the details.

Checklist before you send

1. Open the protected file yourself and confirm the password works.
2. Check you are sending the protected copy, not the original.
3. Send the password through a different channel.
4. Tell the recipient which viewer to use if they have trouble.
5. Keep the original in a safe place.

Frequently Asked Questions

How strong is the encryption?

Protect PDF uses PDF password encryption. The real-world strength comes down mostly to your password: a long, unique passphrase is far safer than a short one.

Can I recover a forgotten password?

No. Keep the original file and store passwords securely.

Will the recipient need special software?

No. Any modern PDF viewer, including browsers, phone apps and Adobe Reader, will ask for the password.

Is it safe to upload a private file to protect it?

Files travel over an encrypted connection and are deleted automatically after processing. For extremely sensitive material, follow your organisation's own security rules.