Protect PDF with password
Lock a PDF so it needs a password to open. AES-256, in your browser.
How to use it
- Drop one or more PDFs onto the page.
- Type a password twice. Use 12 characters or more, or a few random words.
- Press Protect PDF and download the locked file. Keep your original, and keep the password somewhere safe.
Questions
How strong is the lock?
The file is encrypted with AES-256, the standard strong cipher for PDFs. What decides how hard it is to open without the password is the password itself. Someone who has your file can try passwords on their own computer without limit, so a short or common password can be found. Use a long one.
What if I forget the password?
Then the file cannot be opened. The password is not stored anywhere and there is no way to reset it. Keep an unlocked original in a safe place.
Which programs open the result?
Any program that supports PDF passwords, from about 2010 on for AES-256, and from about 2005 on for AES-128. We tested the result with qpdf, pikepdf, pypdf, poppler and PDF.js in a browser. Adobe Acrobat, macOS Preview and Microsoft Edge were not available for testing, so try the file in the program you will use.
Does it change the pages?
No. Text, pictures, fonts, forms, links and bookmarks are copied as they are and then encrypted. The one thing that is lost is a digital signature, because it covers the exact bytes of the file, and any change makes it invalid. You get a warning when a file has one.
Does it work on a PDF that already has a password?
Not directly. Use Remove PDF password first, then lock the result with a new password. To keep the old password and change what is allowed, use Change PDF permissions.
Can I use accents and other letters in the password?
With AES-256 any letters work. With AES-128 the password can only use letters of the Western European alphabet (such as é, ü and ñ), because that is how the older format stores it.
Is my PDF or password uploaded?
No. The file is locked in your browser, on your device.
Are my files uploaded anywhere?
No. This tool runs in your browser, so your files stay on your device and are never sent to a server.
Is it free?
Yes, you can use it for free. A subscription removes limits and unlocks premium tools.