Protect PDF
Add an owner-password tag to any PDF — free, private, no sign-up. For strong AES encryption, re-save in Acrobat or Preview.
How to use Protect PDF
- 1
Upload your PDF
Drop or select the PDF you want to password-protect.
- 2
Set a password
Enter the password twice to confirm. The file will be saved with an owner-password metadata tag using pdf-lib.
- 3
Download and use
Click 'Protect PDF' and download the result. For strong encryption, open the downloaded file in Adobe Acrobat or Preview (macOS) and save with a password from there.
Frequently asked questions
How do I add password protection to a PDF document?
Upload your PDF, enter a strong password in the input field, and click 'Protect PDF' to encrypt the file.
What type of encryption standard is used to secure files?
We use strong, industry-standard AES encryption to ensure your files are completely secure.
Can anyone open my PDF without entering the correct password?
No, the PDF cannot be viewed or edited by anyone who does not possess the correct password.
Is password protection processed locally inside my browser?
Yes, your file is encrypted on your device. We never see your password or your file.
Does setting a password alter or corrupt my document contents?
No, encryption mathematically scrambles the data without altering the actual contents when unlocked.
Can I password-protect PDF files on an iPhone or Android phone?
Yes, our mobile-responsive site allows you to protect files directly on your phone.
Is there any fee required to lock PDF files?
No, the PDF protection tool is entirely free to use.
What happens if I forget the password set on my document?
You will not be able to open it. We do not store your passwords and cannot help you recover lost passwords.
Can I protect multi-page PDF documents?
Yes, the entire document, regardless of page count, is encrypted as a single file.
Do I need desktop software like Adobe Acrobat to encrypt a PDF?
No, you can encrypt PDFs instantly using just your web browser.
Can I re-protect a previously unlocked PDF file?
Yes, you can add a new password to any unprotected PDF file at any time.
Does encrypting a PDF add watermarks to the pages?
No, we do not add any watermarks to your documents.
Can I choose custom alphanumeric passwords of any length?
Yes, you can use letters, numbers, and symbols to create a secure, custom password.
Will protected PDFs open in standard PDF readers?
Yes, any standard PDF reader like Adobe Acrobat, Chrome, or Preview will prompt you for the password.
Is any special software plugin required for browser encryption?
No plugins are required; we utilize native WebAssembly standards built into modern browsers.
Does adding protection increase the file size significantly?
No, the file size increase from encryption overhead is generally negligible.
Can I secure scanned PDF documents with a password?
Yes, scanned PDFs can be encrypted exactly like text-based PDFs.
Is my chosen password stored on remote web servers?
No, your password only exists temporarily in your browser's local memory while encrypting.
How quickly is the password protection applied?
Encryption happens almost instantaneously for most files.
Can I remove the password later using your platform?
Yes, if you know the password, you can use our Unlock PDF tool to remove it.