Protect PDF — Add Password to PDF Files Online Free
Free online PDF protection tool to add password security to your documents. Encrypt PDFs with user passwords and set owner permissions for printing, copying, or editing. Secure sensitive files instantly — 100% client-side, nothing uploaded.
100% client-side. Your PDF is encrypted entirely in the browser — nothing is uploaded to any server.
Passwords
Owner (admin) password
Override permission restrictions
Permissions
What users can do after opening
Print (low quality)
Allow low-res printing
Print (high quality)
High-res printing
Copy text & images
Select and copy content
Modify content
Edit the PDF
Add annotations
Comments and markups
Fill form fields
Fill interactive forms
Assemble document
Insert/delete pages
Drop a PDF file here
or click to browse
Remember your password. There is no way to recover a forgotten PDF password. Save it in a password manager.
How PDF Protection Works
User password — required to open the PDF. Key derived via MD5 (50 rounds) then RC4-128 encryption is applied to all content.
Owner password — separate admin password that can bypass permission restrictions.
Permissions — restrict printing, copying, editing, and annotations even after the PDF is opened.
Compatibility — RC4-128 (PDF 1.4) is the most widely supported encryption format, accepted by every PDF viewer.
How to Use Protect PDF
Upload a PDF
Drop or upload the PDF file you want to password-protect.
Set passwords
Enter a user password (required to open) and optionally an owner password (admin access).
Configure permissions
Set what users can do after opening: printing, copying, modifying, annotating, and form filling.
Download protected PDF
Click 'Protect PDF' and download your encrypted file — all encryption happens locally in your browser.
Frequently Asked Questions
PDF Standard Security Handler r3 with RC4-128 encryption. This is the most widely compatible format supported by every major PDF viewer.
The user password is required to open the PDF. The owner password is an optional admin password that bypasses permission restrictions.
No. There is no way to recover a forgotten PDF password. Always save passwords in a password manager.
Printing (low or high quality), copying text and images, modifying content, adding annotations, filling forms, and assembling pages.
Yes. RC4-128 encryption is supported in Chrome, Firefox, Edge, Safari, Adobe Acrobat, and Apple Preview.
No. All encryption is performed locally in your browser using pdf-lib. Your file never leaves your device.
Yes. Use the Unlock PDF tool if you know the password. Always keep a backup of the unprotected original.
Try an Example
Sample file
confidential_document.pdf
1 file encrypted with user password and restricted printing
Password-protected PDF ready for distribution
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