Protect or unlock PDF
Add a password to a PDF, or remove one you know. The file and the password stay on this device.
This file’s internal structure was damaged. pdfMB rebuilt it while saving, so check that every page looks right.
Working on the lock…
Working on your device. Nothing is uploaded.
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Write the password down now. Without it, nobody, including us, can open this file again.
Send the password a different way from the file. For example, email the file and tell them the password by phone.
This file’s internal structure was damaged. pdfMB rebuilt it while saving, so check that every page looks right.
Download PDFNeed it smaller too? Compress the original first, then lock the smaller file. Compress PDF
If the file is yours, open it in the app that created it and save it again without restrictions.
- No uploadYour file stays on this device.
- Your original stays as it isYou download a new copy. Your file is never changed.
- Free, no sign-upNo account and no daily limit.
What happens to your file
Everything below happens inside your browser, on your own device. The PDF and the password are never uploaded, so nobody else, including us, can see them.
- pdfMB checks whether the PDF already has a password, and shows the right option.
- Locking uses AES-256, the strongest encryption in the PDF standard. Without the password, the file cannot be opened in any PDF reader.
- Unlocking needs the password. pdfMB cannot guess or break a password.
- Text, images, links, bookmarks and form fields are kept exactly as they were.
- The password is used only while the file is being processed, and the fields are cleared straight after.
- Choose a PDF
- Type a new password, or the current one
- Press the button
- Download
How to protect or unlock a PDF
- Choose a PDF. pdfMB tells you whether it is locked.
- To lock it, type a new password twice. To unlock it, type its password.
- Press the button and download the new PDF.
When people use it
Sending private documents
Lock payslips, contracts or medical papers before emailing them, and share the password another way, such as by phone.
Removing a password you no longer need
Bank statements and e-tax receipts often come locked. Unlock a copy so it opens without typing the password every time.
Before using other tools
Most tools cannot work on a locked PDF. Unlock it first, then compress, merge or split it.
What it can’t do
- It cannot unlock a PDF without its password, and it never tries to guess one.
- Files that open without a password but whose owner has restricted copying or editing are not changed.
- A digital signature in the PDF is no longer valid after the file is locked or unlocked.
- Some old PDF readers cannot open AES-256 files. Current versions of Adobe Reader, browsers and phone apps can.
Questions about PDF passwords
How strong is the protection?
pdfMB uses AES-256, the strongest encryption the PDF standard offers. The weak point is usually the password, so use a long one that is hard to guess.
I forgot my password. Can you unlock the file?
No. Without the password the file cannot be opened, and pdfMB does not try to crack passwords.
Can I use Thai or other non-English characters in the password?
Yes. AES-256 supports passwords in any language. Make sure whoever opens the file can type the same characters.
Are the file or the password sent anywhere?
No. Both stay in your browser while the file is processed.
Can I stop people from printing or copying text?
Yes, under “More options”. These settings ask PDF apps to block printing or copying, and most apps follow them, but some ignore them. Anyone with the password can still open and read the file.