Protect PDF

Encrypt a PDF with a password so only people who know it can open the file. Optionally block printing, copying or editing.

PDF ToolsProcessed locallyNo account needed

Drop a PDF to protect

Adds AES-256 encryption. The PDF and password never leave this device.

PDFUp to 100MB100% Private

How to use Protect PDF

Simple steps to get your task done in seconds

Open your PDF

Drop the PDF to protect.

Set a password

Type it twice and choose what readers may do after opening.

Download

Save the encrypted PDF.

How Client-Side PDF Password Protection Works

ZapPebble encrypts your PDF files using the industry-standard AES-256 (Advanced Encryption Standard) cipher via the client-side @cantoo/pdf-lib engine. You can configure user passwords (required to view the file) and granular document permissions (controlling whether recipients can print, copy text, or edit content). Because encryption happens inside your browser, neither your password nor your document is ever exposed over the internet.

Security Property	Specification	Technical Verification
Encryption Standard	AES-256	Standard PDF Revision 6 encryption compatible with Adobe Acrobat, Apple Preview, and modern browsers.
Owner Password	24-Byte Cryptographic Nonce	Generated using `window.crypto.getRandomValues` to prevent permission tampering.
Permission Toggles	Printing, Copying, Editing	Restricts text copying to the clipboard or high-res printing if selected.

Practical Example: Encrypting a Financial Statement for Email Delivery

Document & Security Goal

You are emailing a 5-page employee compensation review Q3_Payroll.pdf to the finance team. Company policy mandates that salary files sent via email must be password-protected with text-copying disabled.

Settings: Set strong password · Check "Allow printing" · Uncheck "Allow text copying".

Verified Encryption Result

The PDF payload is encrypted using AES-256 in less than 1 second.
Opening the file in any PDF reader prompts for the password immediately.
Text selection and clipboard copying are locked down in compliant PDF viewers.

Important Limitations & Password Recovery

No Password Recovery

Because ZapPebble operates with true zero-knowledge client encryption, there is no back-door or recovery service. If you forget your password, the file cannot be decrypted by us. Keep a secure backup of your password.

Permission Enforcement

Standard PDF permissions (copying/printing locks) are enforced by compliant PDF readers (Adobe Acrobat, Preview, Edge). Some basic third-party readers may display content without enforcing permission flags.

Zero Transmission

Neither your password nor your document bytes are ever sent to an external server. The cryptographic keys are derived locally in browser RAM and flushed upon download.

Password GeneratorGenerate cryptographically strong, high-entropy passwords for your PDF encryption.

Unlock PDFNeed to remove password encryption from a document you own? Use the Unlock PDF tool.

Merge PDFCombine multiple documents together before protecting them with a single password.