How to Password Protect a PDF
Learn how to add password protection to any PDF file online for free. Set open and permission passwords with 256-bit AES encryption. No software needed.
About How To Protect PDF With Password
Password-protecting a PDF restricts opening, printing, or copying its content. PDF AI Tools applies AES-128 encryption entirely in the browser so your document remains private before and after protection — no server ever receives your file.
Set separate owner and user passwords: the user password controls opening access while the owner password controls permissions (print, copy, annotate). Most free tools set only one.
How to Use How to Password Protect a PDF
- Step 1: Upload your PDF to Protect PDF
- Step 2: Enter an open password and optionally an owner password
- Step 3: Choose which permissions to restrict (print, copy, edit)
- Step 4: Click Protect and download the encrypted PDF
Key Features
- AES-128 encryption for robust protection
- Separate owner (permission) and user (open) passwords
- Restrict printing, copying, and annotation independently
- In-browser encryption — file never leaves your device
- Protects PDFs of any size
- Compatible with Adobe Acrobat and all standard PDF viewers
- Instant processing
- No ads or watermarks
How We Compare
Compared to desktop alternatives like Adobe Acrobat Pro (starting at $19.99/month), Smallpdf ($12/month for unlimited), or iLovePDF ($9/month Premium), PDF AI Tools delivers comparable quality at $0 for the core feature set. We skip the subscription friction by processing most operations directly in your browser with WebAssembly — no server infrastructure costs to pass on to users. Our AI features (summarization, chat, OCR) use a pay-as-you-go backend that keeps your total cost well under $5/month even for power users.
Frequently Asked Questions
How strong is AES-128 encryption?
AES-128 is government-grade encryption adequate for most business documents.
Can a password-protected PDF be cracked?
With a strong password (12+ characters, mixed case, numbers) brute-force attacks are infeasible.
What is the difference between user and owner password?
The user password is required to open the file. The owner password controls what the opener can do.
Can I remove the password later?
Yes — use the Remove Password tool with the correct password to decrypt.
Who Uses This Tool
- Protect a confidential salary report before emailing
- Lock a legal agreement so it cannot be copied
- Secure a financial statement for client delivery
- Prevent unauthorized printing of a proprietary document