Yes. Protect PDF is free and works without an account, for files up to 25 MB and 150 pages. A free account raises that to 50 MB and 400 pages.

Are my files uploaded to a server?

No. Protect PDF runs in your web browser, so the file is read on your own device and never sent to ConvertFile.

What encryption does Protect PDF use?

AES-256. The password is used only in your browser; we never see or store it. If you lose the password, the file cannot be recovered.

Does Protect PDF work on Mac, Windows, Android and iPhone?

Yes. It runs in any modern web browser, with nothing to install. Very large files work best on a desktop or laptop, because in-browser tools use your device's memory.

Protect PDF

Add a password so the file can't be opened without it.

Runs in your browser. Your file is never uploaded.

Protect PDF in short

Add a PDF, type a password of at least 6 characters twice, and download. The file is encrypted with AES-256, the strongest encryption the PDF standard offers, and nobody can open it without the password, including us. Encryption happens in your browser, so neither the file nor the password is sent anywhere. If you lose the password, the file can't be recovered.

How to use Protect PDF

1Add a PDF.
2Choose a password and confirm it.
3Download the encrypted file.

Good to know

Files are encrypted with AES-256. We never see or store your password.
If you lose the password we cannot recover the file.
This tool runs in your browser. Very large files depend on your device's memory.

Protecting a 3-page document

We protected a 3-page text PDF with a 13-character password and inspected the result.

Protecting a 3-page document
	Before	After
File size	7.0 KB	8.1 KB
Encryption	None	AES-256 (PDF security revision 6)
Opens without the password	Yes	No
Printing and copying once opened	Allowed	Allowed

A 5-character password was refused with "Use a password of at least 6 characters." Measured on 1 November 2026 by running this page's code on sample documents we generated ourselves.

Limits

Without an account: files up to 25 MB and 150 pages. With a free account: 50 MB and 400 pages.
This sets an open password. It doesn't add print or copy restrictions, because many readers ignore them and they can stop the rightful reader from printing.
AES-256 needs Acrobat Reader X (2010) or later, or any current browser, Preview or phone viewer. Very old PDF software may not open the file.
Protecting rewrites the file, so an existing certificate-based digital signature will show as invalid.

What happens to your file

Protect PDF runs in this browser tab. The PDF and the password stay on your device; the encrypted copy is created here and handed back as a download. We record only that the tool was used, never the file, its name or the password.

If something goes wrong

I forgot the password: There's no way back. We never see the password, and AES-256 can't be broken by guessing a reasonable one. Keep the unprotected original somewhere safe.
How long should the password be?: Six characters is the minimum the tool accepts, not a good choice. A short phrase of three or four unrelated words is far stronger and easier to type.
How do I send the password?: Not in the same email as the file. Send it by text message or tell the person by phone, so one intercepted message isn't enough.

Guides

How to password-protect a PDF
Add a password to a PDF with AES-256 encryption, free and in your browser. Plus how long the password should be, how to send it safely, and the Word and Mac options.
How to remove a password from a PDF
Take the password off a PDF you can already open, in your browser and for free. Covers open passwords, permission passwords, and what to do if you've forgotten it.

Protect PDF: common questions

Is Protect PDF free?: Yes. Protect PDF is free and works without an account, for files up to 25 MB and 150 pages. A free account raises that to 50 MB and 400 pages.
Are my files uploaded to a server?: No. Protect PDF runs in your web browser, so the file is read on your own device and never sent to ConvertFile.
What encryption does Protect PDF use?: AES-256. The password is used only in your browser; we never see or store it. If you lose the password, the file cannot be recovered.
Does Protect PDF work on Mac, Windows, Android and iPhone?: Yes. It runs in any modern web browser, with nothing to install. Very large files work best on a desktop or laptop, because in-browser tools use your device's memory.