Protect PDF
Free online tool to password protect a PDF with strong AES-256 encryption. Set an open password that is required to view the file, and optionally add separate permissions that block printing, copying or editing. Everything happens in your browser - your PDF and your password are never uploaded to any server, so sensitive documents stay 100% private. Includes a live password-strength meter, a one-click strong-password generator and a first-page preview. No sign-up, no watermark and no file-size limits beyond your own device memory. Works on desktop and mobile.
Drop your PDF here
or tap to choose it — then set a password and download an encrypted copy
📄 Choose a PDF file🔑 Set the document password
Let people open the file but stop them from doing these things. Tick an action to allow it; untick to block it.
Your PDF is now password protected
⚠ Keep your password safe — it cannot be recovered.
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Protect PDF
The Protect PDF tool adds password encryption to a PDF file — right inside your browser. Choose a PDF, set an open password that anyone must type to view it, optionally block printing, copying or editing, and download an encrypted copy. Because the encryption runs locally on your device, your file and your password are never uploaded to any server, which makes it safe for contracts, bank statements, medical records, payslips and any other confidential document.
How to Password Protect a PDF
- Add your PDF. Drag your PDF onto the drop area or click Choose a PDF file. It is read in your browser and stays on your device.
- Set an open password. Type the password needed to open the file, then type it again to confirm. Watch the strength meter, or hit 🎲 Generate for a strong random password and ⧉ Copy to save it.
- Restrict permissions (optional). Open 🛡 Advanced permissions to let people read the file but block printing, copying text or editing — enforced with a separate owner password.
- Protect and download. Click 🔒 Protect PDF and your encrypted document downloads instantly. Store the password somewhere safe — it cannot be recovered.
Open Password vs. Permissions — What's the Difference?
A PDF supports two independent kinds of protection, and this tool exposes both:
Required just to open and read the document. Without it the PDF cannot be viewed at all. This is what most people mean by "password protecting" a PDF.
Lets people open the file but stops them from printing, copying text or editing it. Enforced with a separate owner password so recipients can't simply remove the limits.
What Makes This Protect PDF Tool Different
No upload, no cloud processing, no account. The encryption runs in JavaScript on your own device, so your confidential file and your password never leave your computer or phone.
A live meter rates your password as you type, and one click creates a strong random 16-character password that skips easily-confused characters.
Go beyond a single password: allow high- or low-quality printing, or block printing, copying, editing, comments and form filling individually.
A responsive layout means it works just as well on a phone as on a desktop, with a first-page preview and no app to install.
How Strong Is the Encryption?
Your PDF is encrypted with 256-bit AES, the strongest scheme defined by the PDF standard and the same algorithm used to protect banking and government data. Your password is converted into an encryption key in your browser and used to scramble the file's contents, so the document genuinely cannot be opened without the password — it is real encryption, not a cosmetic "lock" that a viewer can ignore.
Common Uses
Send a payslip or tax form to an accountant, share a signed contract that recipients can read but not alter, email medical results or legal documents securely, protect an e-book or paid report from casual copying, or lock a scanned ID before storing it in the cloud.
Frequently Asked Questions
Is this Protect PDF tool free and private?
Yes. It is completely free and runs entirely in your web browser. Your PDF file and your password are never uploaded to any server, so they stay private on your own device. The protected PDF has no watermark and needs no sign-up.
What encryption does it use?
The tool encrypts your PDF with 256-bit AES, the strongest encryption in the PDF standard. The password is turned into an encryption key in your browser and the file contents are encrypted, so the PDF cannot be opened without the password.
What is the difference between the open password and permissions?
The open password is required to view the PDF at all. Permissions are a separate layer that can let people open the file but stop them from printing, copying text or editing it. Permissions are enforced with an owner password so recipients cannot simply lift the restrictions.
Can I recover the file if I forget the password?
No. There is no back door and nothing is stored on a server, so a forgotten password cannot be recovered. Always keep a copy of the original unprotected PDF and store the password somewhere safe, such as a password manager.
Will the protected PDF open on any device?
Yes. The output is a standard encrypted PDF, so it opens in Adobe Acrobat, Preview on Mac, Chrome, Edge and mobile PDF readers. Each one will prompt for the password before showing the document.
Can it protect a PDF that is already password protected?
No. An already-encrypted PDF must be unlocked first — the tool detects this and asks you to remove the existing protection before adding a new password.
Are there any file size limits?
There is no fixed limit. Because the encryption happens in your browser, the only practical limit is your device's memory. Files of tens or even hundreds of megabytes work fine on a modern computer or phone.
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"Protect PDF" 於 https://MiniWebtool.com/zh-tw/pdf加密/，來自 MiniWebtool，https://MiniWebtool.com/
by miniwebtool team. Updated: Jul 14, 2026