Protect a PDF with a password or unlock it
To protect a PDF, drop it in, choose a password, and click Protect PDF: the file is encrypted with 128-bit AES in your browser and will ask for that password whenever it opens. To unlock one, enter the password you already have and get an unprotected copy. Nothing is uploaded to a server.
- ✅ Free
- 🔒 No sign-up
- 📱 Works on mobile
- ⚡ Instant results
🔒 Everything runs in your browser. Your data and files never leave your device.
📌 Key facts
- The tool encrypts your PDF with 128-bit AES using the standard PDF security handler.
- A protected file asks for the password every time it opens, in Adobe Reader, browsers, Preview on Mac and mobile viewers.
- An 8-character lowercase password offers about 2×10^11 combinations; 12 characters from 70 symbols offer about 1.4×10^22.
- The open password is required to read the document; the owner password lets someone change print, copy and edit permissions.
- To unlock a file you need to know its password: the tool does not guess codes or crack protection.
- Everything runs in your browser (200 MB maximum), so the PDF never reaches a server.
How a password protects your PDF
The tool uses the PDF standard security handler with 128-bit AES encryption, which Adobe Reader, browsers, Preview on Mac, and mobile viewers all understand. Every piece of text, every image, and every other object in the file is encrypted with a key derived from your password: without it, the content is unreadable.
| Password | Role |
|---|---|
| Open | Required to read the document |
| Owner | Lets someone change permissions (printing, copying, editing) |
\[ \text{file key} = \operatorname{MD5}(\text{padded password} + O \ \text{entry} + \text{permissions} + \text{document ID}) ,\ \text{then} \ 50 \, \text{more MD5 rounds} \]
Choosing a strong password
- Use at least 12 characters mixing letters, numbers, and symbols, or a phrase of several words.
- An 8-character lowercase code (26 options per character) gives about 2×1011 combinations, which is quick to crack; 12 characters from 70 symbols give about 1.4×1022.
- Don't put it in the same email as the PDF: send it through another channel.
- Create it with our Password generator and keep it in a password manager.
Unlocking a PDF: what is possible
You can remove protection if you know the password: the tool checks the code, decrypts every object, and saves an unprotected copy. It doesn't guess passwords or crack protection.
- RC4 128-bit and AES 128-bit: decrypted directly, so text stays selectable.
- Other cases (40-bit RC4, 256-bit AES, compressed structure): after verifying the password, pages are copied as images. The result is readable but the text is no longer selectable.
How to protect a PDF with a password
First, open the tool and drop in your file. Then type an open password and confirm it. Finally, click the button to protect your PDF.
- First, choose the "Protect with a password" mode.
- Then drop in your PDF (200 MB maximum).
- Next, type the open password, and type it a second time to confirm.
- After that, decide the permissions: print, copy text, edit and annotate.
- Finally, download the file. Its name ends with "-protected".
Keep the original in a safe folder. If you lose the password, nobody can reopen the encrypted copy, and Outilix can't either.
Open password or owner password?
A protected PDF can carry two codes. Usually the first one is enough. However, the second one controls what readers can do with the document.
| Code | When to use it | Effect |
|---|---|---|
| Open | the content is confidential | without it, nobody reads the PDF |
| Owner | you want to limit printing or copying | it lets someone change the permissions |
If you leave the owner field empty, the tool generates a random code nobody knows. That way the restrictions hold, but you can't lift them later. Also, remember that common viewers respect these limits, yet they are not unbreakable.
Mistakes people make when they protect a PDF
- Sending the password in the same email as the PDF: use another channel, such as a text message.
- Choosing a short code, because an 8-letter lowercase password falls fast.
- Believing print restrictions stop everything, since a lenient viewer may ignore them.
- Overwriting the original: keep an unprotected copy in a vault or a password manager.
Think about the order of steps too. Merge, split and compress first, then protect the file last. Otherwise, the other tools can't open the encrypted PDF.
Related tools can help: merge PDFs, split a PDF and compress a PDF. To build a strong code, use the password generator. Finally, you can sign the document before you lock it.
Which documents should you protect?
It makes sense to protect a PDF whenever the content is personal. For example, a bank statement, a contract, a medical file or a resume with your home address deserves a password. On the other hand, a public brochure doesn't need one.
Before you send it, open the encrypted copy in your viewer. Then you know the password works. As a result, the recipient doesn't lose time, and you skip a follow-up.
3 real-life examples
Emailing a pay stub
You protect the PDF with the password "Maple-Bike-2026!" (16 characters), email the file, and text the password. If the email is intercepted, the contents stay unreadable.
A statement your bank locked
Your bank sends a PDF that asks for the last four digits of your SSN. You enter them in Unlock and get a copy with no password that you can file or attach to an application, while keeping the original somewhere safe.
Blocking printing
You leave only Copy text checked and uncheck Print. Common viewers gray out the print button. It's a deterrent, not a guarantee: some software ignores these restrictions.