Protect PDF with a Password
Add a password to a PDF with AES-256 encryption. Everything runs in your browser — your file and password are never uploaded anywhere.
Drop a PDF file here, or click to browse
It stays on your device — nothing is uploaded.
At least 4 characters. There's no way to recover a forgotten password.
Before that attachment goes out
Dana works in HR, and the offer letter in front of her has a salary, a signing bonus and a start date. Email is not a locked drawer. If the message lands in the wrong inbox, the password on the PDF is the only thing standing between a stranger and those numbers.
This tool puts that password on, using AES-256 encryption, so the file needs it to open. And because the encryption runs here, the unprotected letter and the password you choose are never handed to a third party just to get locked.
How to password protect a PDF
- Drop the PDF into the box above, or click it to pick the file.
- Type a password into the "Password" field, then repeat it in "Confirm password". Use "Show" to check for typos.
- Press "Protect PDF" and download the locked copy. Your original stays as it was.
What happens to your password
The password is typed into your browser and used there to scramble the document. It isn't sent anywhere, which is also why nobody, including us, can look it up for you later.
The same password is set as both the opening password and the owner password, so anyone who can open the file has the same access. The tool doesn't add print or copy restrictions.
Watch out for lost passwords and weak ones
There's no "forgot password" button. Lose the password and the encrypted file is unrecoverable, so store it in a password manager before you send the PDF. Keep your unprotected original somewhere safe too.
The tool accepts anything from 4 characters, but AES-256 can't make up for a guessable password like 1234. Aim for a long passphrase, and send it through a different channel than the file, such as a text message.
- No upload
- Your PDF and password are processed locally in your browser — nothing is sent to a server.
- AES-256 encryption
- The strongest cipher recommended by the current PDF standard (ISO 32000-2).
Sources
- ISO 32000-2:2020, Document management: Portable document format, Part 2: PDF 2.0 — International Organization for Standardization
- Web Crypto API — MDN Web Docs
Questions
What does AES-256 encryption mean, in plain terms?
It's a scrambling method that uses a 256-bit key, and it's the strongest option in the current PDF standard, ISO 32000-2. Without the password, the contents are unreadable, and guessing the key by brute force isn't realistic. The weak link is usually the password you pick, not the cipher.
What's the difference between a user password and an owner password?
In a PDF, the user password is what opens the file, and the owner password controls permissions like printing or editing. This tool sets the same password for both and adds no permission limits, so think of it as one lock on the front door.
What happens if I forget the password?
The file can't be opened. This tool never stores or sends your password, so there's nothing to recover it from. Keep it in a password manager and hold on to an unprotected original.
Can I protect a PDF that already has a password?
Not directly. The tool needs to read the file first, and an already encrypted PDF will be rejected as unreadable. Remove the old password in a PDF reader, then protect the open copy here.
Will every PDF viewer open the protected file?
Modern readers, including current browsers, Acrobat and Preview, prompt for the password and open AES-256 files. Very old software from the Acrobat 8 era or earlier may not support it, so test with your recipient's setup if it matters.
Are my files or password uploaded anywhere?
No. Your PDF is read and encrypted in your browser, and neither the file nor the password goes to a server. The protected copy is created on your device and downloaded from there.