🔒 PDF Tools
Password-Protect a PDF
Add a password to a PDF so only people with the password can open it. The file is encrypted with strong AES-256 right in your browser — set your password and download the protected PDF, with nothing uploaded.
✓ Free forever✓ No upload✓ No signup✓ In your browser
Quick answer: To password-protect a PDF, drop the file, type the password you want to set, and click Protect. The PDF is encrypted with AES-256 using the qpdf engine right in your browser, and you download a protected file that asks for the password before it opens — nothing is uploaded.
How to Password-Protect a PDF
1
Add Your PDF
Drop the PDF onto the tool, or click to browse and select it.
2
Set a Password
Type the password that will be required to open the file.
3
Click Protect
qpdf encrypts the PDF with AES-256 in your browser — nothing uploaded.
4
Download
Download the protected PDF; anyone opening it must enter the password.
Why Use Convertlo?
- 🔒 100% Private — the PDF and password never leave your browser
- 🆓 Free forever — no account, no watermark, no limits
- 🛡️ AES-256 encryption — strong, modern PDF encryption
- 🔑 Open password — the file prompts for the password before opening
- 🧩 Real qpdf engine — industry-standard encryption via WebAssembly
- 📱 Works on mobile — any modern browser, any device
Features
100% Private
No server, no upload — the file and password stay on your device.
AES-256
Strong, modern encryption applied to the whole file.
Open Password
Readers must enter the password to open it.
qpdf Engine
The industry-standard PDF tool, in WebAssembly.
Instant
Encrypts in seconds.
Mobile-Ready
Works on iPhone, Android, tablet, and desktop.
Frequently Asked Questions
Yes — completely free, no limits, no watermarks, and no account required. Convertlo runs entirely in your browser using the open-source qpdf engine compiled to WebAssembly.
The PDF is encrypted with AES-256, the strong modern standard supported by Adobe Acrobat and every current PDF reader. The password you set becomes the open password required to view the file.
No. Encryption happens locally in your browser. Your PDF and the password you choose never leave your device, so the protected file and its key are never exposed to anyone.
There is no recovery — that is the point of real encryption. Store the password somewhere safe, because without it the protected PDF cannot be opened, by you or anyone else.
Yes. Any standard PDF reader — Acrobat, Preview, Chrome, Edge, or a phone's PDF viewer — will prompt for the password and open the file once it is entered correctly.
Unlock it first with the Unlock PDF tool, then protect it again with your new password. Applying a fresh password requires the file to be readable first.