PDF Medic OnlineAdd a password to a PDF
Lock a PDF with a password (AES-256), so only people with it can open the file.
Files never leave your device
How to Protect PDF
- Choose a PDF, or drop it on the box above.
- Type a password in Password, then again in Type it again. Tick Show password to check it.
- Press Protect PDF, then Download. Your original file stays unlocked and unchanged.
What the password does
This tool adds an open password: anyone who opens the new file, in any PDF reader, is asked for it, and without it the pages cannot be read. The file is encrypted with AES-256, the strongest encryption the PDF format offers. Before you get the file, the tool checks that it really is locked with AES-256; if that cannot be confirmed, no file is given to you.
It sets an open password only. It does not add limits such as no printing or no copying, so whoever knows the password can open, print and copy the file.
The password and the file stay in your browser. Neither is sent to us or anyone else.
Choose a password you won’t lose
There is no reset link and no recovery. We never see your password, so we cannot help if it is forgotten, and the site has no way to open the file without it. Before you share the protected copy, write the password down or save it in a password manager.
- Longer is stronger. AES-256 is only as safe as the password: a short or common one can be found by programs that try many guesses.
- Send the password a different way from the file, for example the file by email and the password by text message or a phone call.
- Think about the person opening it. Letters with accents or Arabic letters can be hard to type on another device’s keyboard; plain letters and numbers are easiest.
Files it won’t lock straight away
- The PDF already has a password: remove it first with Unlock PDF using that password, then protect the unlocked copy. This is also how you change a password.
- The PDF has limits set by its owner, such as no editing: only the owner (permissions) password can lift them, in Unlock PDF. The site never removes them any other way.
- The PDF is digitally signed: adding a password rewrites the file, so the signature will show as invalid. Tick the box to go ahead, and keep the original if you may need to prove the signature.
Opening the protected file
Up-to-date PDF readers and web browsers on phones and computers ask for the password and then show the file as usual. Very old PDF software may not support AES-256. The protected file is named after the original with -protected added, so the two are easy to tell apart.
Everything happens in your browser: your file is never uploaded to any server. You can check: once your file is open, turn on airplane mode — the tool still works.
Questions
What if I forget the password?
The protected copy cannot be opened without it, by you or by us. Your original file is still unlocked, so you can protect it again with a new password.
How do I change the password on a PDF?
Remove the old one with Unlock PDF, typing the old password, then lock the unlocked copy here with the new one.
Can I stop people printing or copying from my PDF?
Not with this tool. It only adds a password to open the file. To hide parts of a page from everyone, use Redact PDF instead.
How secure is AES-256?
It is the strongest encryption the PDF format supports. In practice the weak point is the password, so use a long one that is not easy to guess.
Can I protect several PDFs at once?
One file at a time. To send several documents under one password, join them first with Merge PDF, then protect the merged file.
Is my file uploaded?
No. Protect PDF runs in your browser on your own device. The file is never sent to our server or anyone else. Once your file is open you can even turn on airplane mode.
Is it free?
Yes. No sign-up, no limits on how many files, and no watermark is added to your file.
Does it work on a phone?
Yes, in any modern browser on iPhone, Android, Mac, Windows or Linux. Very large files work best on a computer, because a phone browser has less memory.