How to Password Protect a PDF File for Free

How to add a password to a PDF online for free

PDFSpot encrypts your PDF with a strong password using 256-bit AES encryption — the same standard used by banks and governments.

1. 1Go to the Protect PDF tool above.
2. 2Upload the PDF you want to protect.
3. 3Enter a strong password in the password field.
4. 4Click Protect PDF and download your encrypted file.
5. 5Share the PDF and the password separately — never in the same message.

What encryption does PDFSpot use?

PDFSpot applies 256-bit AES encryption (PDF standard revision 6), which is the highest level of PDF encryption currently defined in the PDF specification. This is computationally infeasible to brute-force with modern hardware when a strong password is used. For context, it would take billions of years to crack a properly chosen password with this encryption.

How to choose a strong PDF password

The encryption is only as strong as the password. A weak password like "1234" or "password" can be cracked in seconds by anyone with basic tools. Use these guidelines for a strong password:

At least 12 characters long.

Mix of uppercase, lowercase, numbers, and symbols.

No real words, names, or dates.

Example of a strong password: Tx7#mK2!vQpL

If the document is highly sensitive, use a password manager to generate and store the password.

How to share the password safely

The most common mistake is sending the password in the same email as the protected PDF — if anyone intercepts that email, they have both. Best practices for sharing:

Send the PDF by email, then share the password by phone, SMS, or a separate messaging app.

Use a one-time password link service for very sensitive documents.

For legal or financial documents, consider using a secure document signing platform for the most sensitive exchanges.

Difference between open password and permissions password

When you protect a PDF with PDFSpot, you set an open password — anyone who wants to view the file must enter it. This is the most common type of PDF protection.

Permissions passwords (also called owner passwords) restrict specific actions like printing, copying, or editing without preventing the file from being opened. These are set by document creators in advanced PDF editors. PDFSpot sets both the user and owner password to the same value for simplicity.

How to remove a password from a PDF later

If you need to share an unlocked version later, or if the document no longer needs protection, you can remove the password using the Unlock PDF tool. You will need to enter the original password to remove it.