Protect PDF with a Password
Lock a PDF with strong AES-256 encryption so it cannot be opened without your password. Everything happens in your browser — your file and your password are never uploaded.
Your PDF is encrypted in your browser — nothing is uploaded.
Click to choose a PDF or drag and drop it here
Then set the password to encrypt it with
How it works
When you select a PDF, the tool loads it in your browser and re-writes it with a 256-bit AES encryption layer using qpdf, a mature open-source PDF engine compiled to WebAssembly. The password you choose becomes the key: any PDF reader will ask for it before showing a single page. Because the encryption is performed locally, your document and your password are never uploaded, never logged and never stored anywhere — the protected file is built entirely on your own device and simply downloaded when it is ready.
How to password-protect a PDF
- Click the box above or drag a PDF onto it.
- Type the password you want, then type it again to confirm.
- Click Protect PDF.
- Your browser downloads the encrypted file as
<name>-protected.pdf. - Share the file and give the password to the people who should be able to open it.
Choosing a password you can rely on
The protection is only as strong as the password behind it. A long passphrase — several unrelated words, or a sentence only you would write — is both harder to guess and easier to remember than a short jumble of symbols. Avoid names, dates and anything someone could find on your profiles. Just as important: because the whole process runs on your device with nothing sent to a server, there is no forgot password link and no support team that can let you back in. Save the password in a password manager before you send the file, and never email the document and its password together in the same message.
Why encrypt in your browser
You usually password-protect a PDF precisely because it is sensitive — a contract, a payslip, a medical record, a scan of an ID. Uploading that file to an online encryption service to lock it means handing the unprotected original, and often the password too, to someone else’s server first. This tool never does that: the document is read, encrypted and saved without leaving your machine, no account is required, and the service adds no watermark or trace of its own. Once the page has loaded it works offline as well, so you can lock a confidential file with no connection at all.
Related tools
New here? Read how to merge pdfs without losing quality or browse all our PDF guides.
Frequently asked questions
How strong is the encryption?
Your PDF is encrypted with 256-bit AES, the same modern standard used to lock PDFs in professional tools. A reader will require the password you set before the document can be opened.
Is my PDF or password uploaded anywhere?
No. The encryption runs entirely in your browser using qpdf compiled to WebAssembly. Your file and the password you type never leave your device and are never sent to a server.
Will anyone be able to open the file without the password?
No. Once protected, the PDF cannot be opened or read without the password. Choose a strong one and store it somewhere safe — because nothing is uploaded, there is no way for us to recover it if you forget it.
Does adding a password change the contents of my PDF?
No. The pages, text, fonts and images are left exactly as they were; only an encryption layer is added on top, so there is no loss of quality.
Can I remove the password again later?
Yes. If you know the password you can strip it back off at any time with our Unlock PDF tool, which produces a clean copy with the protection removed.