NOPPAW

Protect PDF

Protect PDF encrypts a document with a password using qpdf — the serious, open-source PDF toolkit — compiled to WebAssembly and running entirely in your browser. The open password is what a reader must type to view the file; an optional separate owner password guards permissions in apps that respect them. Neither the file nor the passwords are ever sent anywhere: the encryption keys are derived on your own device.

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Accepted: PDF · Max 50 MB per file · Processed locally in your browser

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Process a file to view the result summary.

How to use Protect PDF

  1. Choose or drop the PDF.
  2. Type the password a reader will need to open the file.
  3. Optionally set a different owner password; leave it blank to reuse the open password.
  4. Click Protect PDF and download the encrypted copy.

Supported behavior

  • Real AES encryption performed by qpdf (WebAssembly build) — the same engine professionals use on the desktop.
  • Two password levels: a user (open) password and an owner (permissions) password.
  • The encrypted copy opens in any modern PDF reader after the password is entered.

Best for

  • Sending contracts, statements or ID documents through email or chat.
  • Storing sensitive exports in shared cloud folders.
  • Handing a document to a client while keeping control of the master copy.

Limits

  • There is no recovery: if the password is forgotten, the file cannot be opened — we never see it and cannot help. Save it in a password manager.
  • Very old PDF readers may not support current AES encryption; recipients should use an up-to-date reader.
  • Encryption protects content, but file names and the fact a document exists are of course still visible.

Privacy notes

  • Processing happens entirely in your browser, so nothing in your document is sent anywhere.
  • This is the rare password tool where the claim is checkable: encryption runs in your tab via WebAssembly, and you can go offline after the page loads and it still works.

Related tools

Optimize & Edit Unlock PDF Remove password protection from a PDF you have the password for. Optimize & Edit Watermark PDF Stamp diagonal text across every page of a PDF. Optimize & Edit Flatten PDF Flatten form fields into permanent, uneditable page content. Organize Merge PDF Combine several PDFs into one file, in the order you pick.

Related guides

Guide How to Sign a PDF Without Printing It How visual PDF signatures work, when they are enough, where they are not, and how to place and send them well. Updated November 6, 2026 Guide How to Password-Protect a PDF Before You Send It What PDF password encryption really protects, the AES basics, and the one channel rule that makes or breaks the whole exercise. Updated November 6, 2026

Protect PDF FAQ

Is my password sent to your server?

There is no server involved. The password is fed to the qpdf engine inside your browser and the encrypted file is created in memory. Disconnect from the internet after loading the page and try it — it still works.

What is the difference between the user and owner passwords?

The user password must be entered to open and read the file. The owner password controls permission flags (printing, copying) in readers that enforce them — and also opens the file with full rights.

I forgot the password. Can you recover the file?

No — and neither can anyone else without the password or serious brute-force effort. That is what real encryption means. Keep passwords in a password manager.

How strong is the encryption?

qpdf applies AES encryption (256-bit where supported). A long, unique password matters more than the number: use several words or a generated password.