Password Protect a PDF
Add AES-256 encryption to any PDF. The file and the password stay in your browser.
Drop your PDF here
or tap to browse — nothing is uploaded
How to password protect a PDF
- 1
Choose your PDF
Drag the file onto the box above, or tap it to browse. The file is read locally and is never uploaded.
- 2
Set a password
Type a password of at least six characters and confirm it. The strength meter shows how well it would hold up to guessing.
- 3
Pick what's allowed
Decide whether people who have the password may print the document or copy text out of it.
- 4
Download the protected file
Click Protect PDF and save the encrypted copy. Your original file is untouched.
Why encrypt in the browser instead of on a server
The documents people want to password protect are almost by definition the ones they least want on someone else's hard drive: salary slips, tenancy agreements, medical records, board papers, bank statements, tax filings.
The usual online workflow has an awkward gap in the middle. You upload an unprotected file to a stranger's server, that server encrypts it, and you download the result. For the few seconds in between, the plaintext document and the password you chose both exist on hardware you do not control. Most services delete them promptly and most are run by honest people. But the exposure is real, and it is entirely avoidable.
Browsers have shipped the Web Crypto API for over a decade, which means AES-256 can run on your own machine at perfectly reasonable speed. Nothing about this problem requires a server. So there is no upload here — open your network tab and check.
Choosing a password worth using
PDF encryption is only as strong as the password behind it. AES-256 is not the weak point; Passw0rd! is. Offline cracking tools work through common patterns — a capitalised dictionary word, a digit, a punctuation mark — in seconds.
- Four or five unrelated words beat one clever word. copper-harbour-quilt-nine is far stronger than Tr0ub4dor&3 and much easier to relay over the phone.
- Never reuse a password you use for an account. If that account leaks, the document leaks with it.
- Send the password through a different channel than the file. Emailing both together protects nothing.
- Store it in a password manager before you close this tab. There is no reset link.
What password protection does and doesn't do
Encryption stops someone opening the file without the password. It does not stop someone who has the password from screenshotting a page, retyping the contents, or forwarding the file onward. The print and copy restrictions are honoured by well-behaved readers as a convenience, not enforced as a security boundary — some tools ignore them. Treat this as a strong lock on a document, not as rights management.
Frequently asked questions
Is it safe to password protect a PDF online?
On most sites, no — your unprotected file is uploaded to a server, encrypted there, and you have to trust that both the document and the password are deleted afterwards. LockedPDF encrypts the file inside your browser using the Web Crypto API. The PDF and the password never travel over the network, so there is nothing on a server to leak or subpoena.
What encryption does this use?
AES-256, which is the standard modern PDF readers expect. Adobe Acrobat, Preview on macOS, Chrome's built-in viewer and every mainstream mobile reader will prompt for the password normally.
Can you recover my password if I forget it?
No, and that is deliberate. The password is never transmitted or stored anywhere — it exists only in your browser tab while you are using the tool. Write it down somewhere safe before you close the page. A forgotten password on an AES-256 PDF is effectively unrecoverable.
What is the difference between a user password and an owner password?
A user password is required just to open the document. An owner password only restricts actions like printing or copying while still letting anyone open the file. This tool sets both to the same value, which is what almost everyone actually wants — a document that cannot be opened without the password.
Can I protect a PDF that already has a password?
Not directly. Remove the existing password first with the Unlock PDF tool, then come back here and set the new one.
Does this work on a phone?
Yes. It runs in mobile Safari and Chrome with no app to install. Large files take longer on a phone because the encryption uses your device's processor rather than a server.