Protect PDF

How to use Protect PDF

1. 1

   Upload the PDF you want to protect.

2. 2

   Enter a strong password and confirm it.

3. 3

   Click Protect to encrypt the document.

4. 4

   Download the password-protected PDF.

The two passwords a PDF can carry

A PDF supports two distinct passwords, and confusing them is the usual reason protection does not do what someone expected. The user password (or open password) is required to open the document at all — without it there is nothing to see. The owner password (or permissions password) lets anyone open the file freely but restricts printing, copying and editing.

Only the user password is real security. Permission restrictions are a flag inside the file that readers are asked politely to respect, and plenty of readers simply do not. If the content genuinely must not be read by the wrong person, set an open password.

Choosing a password that is worth setting

PDF encryption is AES-256, and it is not the weak point. The password is. A four-digit PIN or a date of birth falls to an offline brute-force attack in seconds, and encrypted PDFs are attacked offline by definition, because the attacker holds the whole file.

Use four or five unrelated words, or a generated string from a password manager. Then send the password through a different channel from the document — a password emailed in the same thread as the file it protects has accomplished nothing at all.

• Long and unrelated beats short and clever: length is what costs an attacker time.
• Never reuse a password you use elsewhere — recipients will see this one.
• Different routes for file and password: email the PDF, message the password.

When to protect, and when to do something else

Protect when a document with personal or financial data has to travel by email, when you are sending someone else's data and are accountable for it under GDPR, or when a file lands somewhere shared and only some people should read it.

Do something else when the recipients are many and unknown — password fatigue guarantees the password gets forwarded — or when you only want to stop copy-paste, which permission flags do not reliably achieve. And never rely on a password for a document you also published elsewhere unprotected.

Encrypting without handing over the file

Every step runs inside your browser, using the WebAssembly and Canvas APIs your device already ships with. No file is uploaded, no copy is kept, and nothing sits in a queue on a server waiting to be deleted — which is also why the tool keeps working with the network disconnected.

There is a particular absurdity in uploading a confidential document to an unknown server in order to make it confidential. Doing the encryption locally means the plaintext document and the password exist only on your machine, which is the only arrangement in which the protection means anything.

Frequently Asked Questions

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