Protect PDF
Encrypt your PDF document with a password using strong client-side encryption. Secure your file instantly.
Password Protection
Selected: document.pdf
Encrypting document locally using AES-GCM...
All calculations are run locally inside your browser context. Please do not close this tab.
Task Completed successfully
Your new file is ready to download.
Executed 100% locally on your browser
When you upload files, they are read as binary arrays in your browser's sandboxed RAM. We use high-performance WebAssembly engines and Client APIs to execute all processing locally. No files are sent to our servers, keeping your documents 100% confidential and secure.
Secure your confidential files. Apply strong password encryption (RC4 or AES) directly inside your browser tab to prevent unauthorized opening or editing.
How to use our free Protect PDF tool
Select PDF document
Select the PDF file you wish to secure by browsing your folders or dragging it in.
Set a strong password
Type your desired password in the security panel. Choose a combination of letters, numbers, and symbols.
Encrypt locally
Click the 'Encrypt PDF' button. The WebAssembly engine compiles the PDF with local cipher encryption.
Download locked PDF
Save the protected PDF file. It will require the password before any PDF reader will open it.
Why Use PDFVoid Protect PDF?
RC4 / AES Security
Applies standard PDF encryption parameters to lock document content streams securely.
Complete Confidentiality
No passwords or unencrypted files are ever transmitted, ensuring absolute safety for keys.
Universal Lock Compatibility
The password protection is fully compliant with Adobe Acrobat, PDF readers, and mobile OS viewers.
Frequently Asked Questions
What happens to the password I type?
Your password stays strictly inside your browser's execution stack. It is used to generate the cryptographic keys to encrypt the PDF array, and is never logged or sent to any server.
Can anyone open my protected PDF without the password?
No. The PDF will be locked using standard compliance algorithms. Standard PDF software will refuse to decrypt the document streams without the correct password.
Is this tool free to use?
Yes, like all PDFVoid tools, securing your PDFs is completely free, unlimited, and runs client-side.