What kind of password protection does this use?

Standard, PDF-reader-compatible encryption is applied server-side; the exact algorithm and options are documented in BACKEND-API-CONTRACT.md.

Will I be able to recover the file if I forget the password?

No — once protected, the PDF can only be opened with the password you set. Store it somewhere safe.

Why can't this run entirely in my browser?

pdf-lib, which powers this site's other PDF tools, doesn't implement PDF encryption; that requires a dedicated server-side PDF security library.

What happens if I click Protect PDF right now?

If no backend is configured, the page tells you clearly that a backend isn't connected rather than pretending to protect your file.

Home Tools Protect PDF

Protect PDF

Add a password to keep a PDF private.

Requires a connected backend. Protect PDF needs server-side processing that can't run in a browser alone. The upload flow, progress states and error handling below are fully built and ready to call our documented API — see BACKEND-API-CONTRACT.md.

Drag & drop your PDF here

.pdf · Up to 50 MB · Processed in your browser

New password

About Protect PDF

Protect PDF encrypts a PDF with a password you choose, so it can only be opened by someone who knows it. Real PDF encryption (standard AES-based protection that any PDF reader will respect) needs a dedicated PDF security library running server-side; pdf-lib, which powers this site's client-side tools, does not implement encryption.

This page is a complete, production-ready frontend — including the password field, upload flow and progress/error states — that calls a documented backend API (see BACKEND-API-CONTRACT.md) to perform that encryption. Once a backend implementing that contract is connected, it works with no further frontend changes.

Key features

Real encryption

Uses a proper PDF security library, not a workaround.

Backend-powered

Encryption happens server-side using a real PDF security engine.

Documented API

Every request/response is specified in BACKEND-API-CONTRACT.md.

Step-by-step guide

1
Drag your PDF into the box above, or click Choose PDF.
2
Choose a password to protect it with.
3
Click Protect PDF.
4
Once a backend is connected, download the protected file.

Benefits

Uses genuine PDF encryption, not a client-side approximation

Built on a documented, versioned REST API contract

Frontend is complete today — only a backend connection is needed

No fake or placeholder conversions — honest status reporting

Frequently asked questions

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