Protect PDF with Password
Runs entirely in your browser
Add a password to a PDF so only people who know it can open it. Your file is encrypted with AES-256 entirely in your browser — it's never uploaded to our servers, and we never see or store your password.
Drag & drop a PDF file here
or
Up to 50MB.
File
This password can't be recovered if you lose it — nobody, including us, ever sees or stores it.
What is Protect PDF?
Protect PDF adds password encryption to a PDF so it can't be opened without the password you choose. It uses AES-256 encryption, the current PDF standard for strong protection, applied entirely on your device. Because the password is never transmitted or stored anywhere, it's essential to remember it — there's no recovery option.
How to use Protect PDF
- Choose a PDF file, or drag and drop it into the tool.
- Enter a password and confirm it.
- Click Protect PDF and download the encrypted file.
Features
- Strong AES-256 encryption, with automatic fallback if your browser can't use it in the current context.
- Password confirmation field to help avoid typos.
- Show password toggle so you can double-check what you typed.
- 100% client-side — your PDF and password never leave your browser.
Example: locking down a financial statement before emailing it
You need to email a PDF of quarterly financial statements to an external accountant. Rather than relying only on your email provider's link security, add a password directly to the PDF with Protect PDF, then share the password with the recipient through a separate channel — a phone call or a different app — rather than in the same email as the attachment.
Things to know
- Passwords must be at least 4 characters — there's no maximum length, so a longer passphrase is accepted and generally stronger than a short password.
- AES-256 protects the file from being opened without the password; it doesn't add a digital signature or watermark, and it can't stop someone who already has the password from sharing the unlocked content further.
- If the PDF you upload is already password-protected, the tool won't double-encrypt it — remove the existing password first with Unlock PDF, then apply a new one.
- AES-256 relies on the browser's Web Crypto API, which is only available in a secure context (HTTPS or localhost). If that's ever unavailable, the tool automatically falls back to the older RC4 cipher and tells you which one was used in the result.
Is Protect PDF safe?
Yes. Protect PDF uses your browser's Web Crypto API to apply AES-256 encryption locally, falling back to RC4 only if a secure context isn't available — your PDF and the password you set are never transmitted anywhere or stored, not even by us.
Frequently Asked Questions
What happens if I forget the password?
There is no way to recover it. Since the password is never stored anywhere, including by us, a lost password means the protected PDF can no longer be opened. Keep it somewhere safe.
What encryption does this use?
AES-256 (PDF 2.0 standard), the strongest widely supported PDF encryption. If your browser can't use AES-256 in your current context, a legacy RC4 mode is used instead so the tool still works, and the result page tells you which one was used.
Does this stop people from printing or editing the PDF?
Setting a password also declares the PDF's permissions to compliant readers. However, PDF permissions are advisory — they're honored by well-behaved PDF software but aren't a cryptographic guarantee against a determined tool. For true confidentiality, rely on the open password itself.
Can this remove a password from a PDF instead?
No, this tool only adds a password. To remove one, use Unlock PDF instead.