Password protect a PDF
Add a password so only people who know it can open your PDF. Free and private.
How to use Lock PDF
- Step 1Choose your PDF.
- Step 2Type a password twice.
- Step 3Download the locked PDF.
Why use DoMyPDF’s Lock PDF
Free to use
Lock PDF is free for 3 files a day with no sign-up and no watermark. Premium removes the daily limit for heavy use.
Private by design
It runs inside your browser, so your file never leaves your phone or computer, and it keeps working on a slow connection.
Works on every device
Use it on iPhone, iPad, Mac or a Windows PC, in any modern browser. Nothing to install, and you can add DoMyPDF to your home screen.
Quality first
Gives you the result in seconds, with no watermark added to your pages.
Tips for the best result
- Lock PDF saves a new copy; your original file isn’t changed, so you can always start again.
- Working on a phone? Large PDFs with many photos are quicker if you compress them first.
- Combine tools for bigger jobs: merge files, then add page numbers, then compress the result.
- Every page stays sharp: text and pictures are kept at their original quality unless you choose to compress.
Lock PDF questions
Is Lock PDF free?
Yes. Every tool is free for 3 files a day, with no sign-up. Premium removes the daily limit.
Is my file safe?
Your file is processed inside your browser and is never uploaded.
Can you recover a forgotten password?
No. We never see your password, so keep it somewhere safe.
Does Lock PDF work on iPhone, iPad and Mac?
Yes. Lock PDF works in Safari, Chrome, Edge and Firefox on iPhone, iPad, Mac and Windows computers, with nothing to install. You can also add DoMyPDF to your home screen to open it like an app.
Is there a file size limit?
No fixed limit: Lock PDF runs on your own device, so it handles files as large as your phone or computer can open. Very large files (over about 100 MB) can be slow on older phones.
Do I need an account?
No. There is no sign-up and no email needed. Open the tool, choose your file and download the result.