Protect PDF
Password-protect and encrypt a PDF online for free with AES-256 — 100% in your browser, so your confidential file and password are never uploaded.
100% private — your PDF and password never leave your browser. Unlike upload-based tools, encryption runs entirely on your device. You can even switch off your Wi-Fi after the page loads and it still works.
Adds Adobe-compatible encryption (AES-256 by default). Because it runs in your browser, your confidential document and its password are never uploaded — a guarantee upload-based tools can’t make. You can even turn off your Wi-Fi after this page loads and it still works. Keep your password safe: without it, the PDF can’t be opened. Note: permission restrictions rely on the PDF reader honouring them — a few non-compliant readers may ignore them, so encryption (a password to open) is the only guarantee for truly sensitive files.
How to use the Protect PDF
- Drop your PDF, or click to choose.
- Enter a password and pick the encryption strength.
- Choose which permissions to allow.
- Click Protect PDF and download it.
What you can use it for
- Password-protect confidential documents
- Encrypt PDFs with AES-256
- Restrict printing, copying or editing
- Secure files without uploading them
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Explore all free PDF tools →Frequently asked questions
Is it safe to password-protect a PDF online?
With most tools, no — they upload your file and your password to a server (even ones that say 'delete after 1 hour' still receive them first). This tool is different: it encrypts entirely in your browser, so your document and password are never transmitted. You can prove it by turning off your Wi-Fi after the page loads — it still works.
Do you ever see or store my password?
No. The password stays in your browser's memory only for the moment of encryption; it's never sent anywhere, logged or saved.
What encryption do you use — is AES-256 secure?
AES-256 by default — the strongest, Adobe-compatible standard, effectively unbreakable by brute force with a strong password. AES-128 and legacy RC4-128 are also available.
What's the difference between AES-256, AES-128 and RC4?
AES-256 and AES-128 are modern, strong ciphers (256-bit is the stronger key). RC4-128 is older and weaker — only use it for compatibility with very old software.
What's the difference between an open password and a permissions password?
An open (user) password is required to view the PDF at all. A permissions (owner) password lets you set what viewers can do — print, copy, edit — without necessarily requiring a password to open.
Can I stop people from printing, copying or editing my PDF?
Yes — uncheck any permission (printing, copying text, editing, comments, form filling) to restrict it.
Will the printing and copying restrictions work in every PDF reader?
Encryption (a password to open) is always enforced. Permission flags rely on the reader honouring them — most do, but a few non-compliant readers may ignore them, so use a strong open password for truly sensitive files.
How strong should my password be, and what if I forget it?
Use at least 8–16 characters mixing letters, numbers and symbols. There's no recovery — if you forget it, the PDF can't be opened, so store it safely.
Will the protected PDF open in Adobe and other readers?
Yes — it uses standard PDF encryption that Acrobat, Apple Preview, Chrome, Edge and other readers support.
Is there a file size limit or a daily usage limit?
No — there's no server, so no upload cap, no '3 tasks per hour' throttle and no batch paywall. The only limit is your device's memory.
Do I need to create an account or pay?
No — it's completely free, with no sign-up, no watermark and no ads.
Does this work on Mac, Windows, iPhone and Android?
Yes — it runs in any modern browser on any operating system.