About Protect PDF
Email is not private. An attachment can sit in several inboxes, backups and mail servers for years. If a document contains anything you would not want a stranger to read, such as a contract, an ID scan, a medical form or a payslip, the sensible thing is to protect the file itself, so that the file is useless without the password.
This tool adds a password to a PDF using AES-256 encryption, which every PDF reader released in the last fifteen years can open. It happens in your browser: neither the document nor the password is sent anywhere. You can also choose whether the person who opens it may print or copy text from it.
How to password-protect a PDF
- Choose the PDF.
- Enter a password in the Password box. It must be at least four characters, and a longer one is much safer. A phrase of several words is easier to remember and harder to guess than a short mix of symbols.
- Optionally set an Owner password. This is a second password that controls permissions. Leave it empty if you do not need it.
- Choose what a reader may do. "Allow printing" is on by default, and "Allow copying text out" is off by default. Change them to suit.
- Press the button and save the protected file. Then open it to check that it asks for the password, before you send it.
When you would use it
- Sending a contract, payslip, tax document or ID scan by email.
- Storing sensitive documents in a shared or cloud folder.
- Giving a client a report that they need a password to open.
- Stopping a document being printed or copied from by the people you share it with.
- Protecting a file on a USB stick that might be lost.
What it will not do
- There is no recovery. If you forget the password, nobody, including us, can get the document back. Keep it in a password manager.
- Send the password by a different route from the file. A password in the same email as the document protects nothing.
- Permissions such as "no printing" and "no copying" are requests that well-behaved programs respect. They are not a lock, and software that ignores them exists. The password to open the file is the real protection.
- A weak password can be guessed. AES-256 is strong, but a four-letter password can be tried by a computer in moments.
- To take a password off a file you own, use Unlock PDF. To remove the hidden author and software details as well, use Remove metadata.
How it compares
Some word processors and PDF programs can encrypt as they export, which is best if you are exporting anyway. This tool adds the protection to a PDF you already have.
Many online services do it by uploading your file and your password to a server, which is exactly the thing you are trying to avoid. Doing it in the browser means the unprotected file and the password stay on your computer.
Tips
- Use a passphrase of four or more unrelated words.
- Test the file in a second reader before you rely on it.
- Keep an unprotected copy somewhere safe, so a forgotten password is an inconvenience rather than a loss.