How to protect a PDF with a password

  1. 1

    Upload your PDF

    Upload the PDF you want to protect.

  2. 2

    Set a password

    Enter the password you want to use. Keep it safe — if you lose it, no one can open the file.

  3. 3

    Download the protected PDF

    Click Protect PDF. Download the password-protected file.

About PDF password protection

Password-protecting a PDF prevents unauthorised access to sensitive documents. Once protected, the PDF requires the password to be entered before it can be opened in any PDF reader. DocumentFlipper applies AES-256 encryption — the same standard used by financial institutions and governments — to lock your document.

The tool supports two levels of protection: a user password that must be entered to open the document, and an owner password that controls permissions such as printing and editing. You can apply both for maximum control, or just a user password for a simple open-to-read restriction.

Your file is processed on our server over a secure HTTPS connection and deleted within two hours. The password is never stored or logged.

Frequently asked questions

What encryption is used?
We apply 128-bit RC4 or 256-bit AES encryption depending on the PDF version — the industry standard used by Adobe Acrobat.
Can I remove the password later?
Yes — use our Unlock PDF tool to remove the password if you know it.
What if I forget the password?
We don't store passwords anywhere. If you lose it, the PDF cannot be recovered — keep your password safe.
Does it restrict editing too?
The open password prevents viewing. Editing and printing restrictions are separate permissions — coming soon as a Pro feature.
Is it free?
Yes — protecting your PDF with a password is completely free with no sign-up required.