How do I password protect a PDF?

Step by step

1. Open the tool. Go to Protect PDF in a current browser on your computer or phone.
2. Select your PDF. Click “Select PDF file” or drop the PDF you want to protect onto the page.
3. Type the password twice. Enter the open password and repeat it to rule out typos. This is the password needed to open the file.
4. Add restrictions if you need them. Optionally restrict printing, copying, editing, comments, forms or page changes. If you do, set a separate permissions password that differs from the open password.
5. Click Protect PDF. Click “Protect PDF”. The file is encrypted with AES-256 on your device.
6. Download and send. Click “Download” and send the protected PDF. Share the password separately, for example by phone or through a different messaging app.

Open password vs permissions password

The tool can set two different passwords. They do different jobs, so it helps to know which one you actually need.

Open password

This password encrypts the whole file. Without it, the PDF can't be opened. According to the tool page, with a long, unique password an AES-256 encrypted PDF can't realistically be opened without the password. This is the protection that matters for private documents.

Restrictions and permissions password

Restrictions ask PDF readers not to allow printing (or only in low resolution), copying, editing, comments, form filling or page changes. The permissions password is needed to lift them, so make it different from the open password.

Most readers respect restrictions, but some ignore them. Treat restrictions as a polite request, not a lock. If the content must stay private, rely on the open password.

Tips for a strong password and safe sharing

• Use at least 12 characters. Three or four random words are long and still easy to type.
• Don't reuse a password from your email or bank account.
• Never put the password in the same email as the file. Send it by phone or through a different messaging app.
• Store the password in a password manager, or keep an unprotected copy of the original in a safe place.

A forgotten password can't be recovered by anyone, including PDF4U. That is what makes the protection strong, and it is also why keeping the original or the password matters.

Compatibility and when to use another tool

AES-256 works in Adobe Acrobat and Reader 9 or later, Chrome, Edge, Firefox, Safari, macOS Preview and current mobile apps. Very old PDF readers may not open the file. If a recipient can't open it, ask them to try a current browser or an up-to-date PDF app.

To remove the password later, use Unlock PDF: select the file and enter the password. You can add a new password again at any time with Protect PDF.

If you want to merge, compress or otherwise change a document, do that before you protect it. Protection should be the last step before you send the file.

Tools used in this guide

• Protect PDF
• Unlock PDF

Related guides

• How to remove a password from a PDF
• How to sign a PDF without printing it
• How do I add a watermark to a PDF?