Protect PDF with password online for free. Encrypt your PDF documents with strong passwords. Secure sensitive documents before sharing via email or cloud. Local encryption.
Upload the PDF file you wish to secure.
Enter a strong password in the input field.
Click "Encrypt PDF" to apply 128-bit AES encryption.
Download your password-protected file.
No — encryption happens locally on your device and we never see your password or file. If you lose the password, the PDF cannot be unlocked. Store it safely.
The tool applies 128-bit AES encryption via the pdf-lib library — the same standard used by Adobe Acrobat for password-protected PDFs.
A user password is required to open the PDF. An owner password restricts printing, copying, and editing but allows opening without a password. This tool sets a user (open) password.
Modern AES-128 encryption is computationally strong. A weak password (dictionary words, short strings) is more vulnerable to brute-force than a long random password. Use at least 12 characters with a mix of symbols.
No — the tool processes the file in memory. Your original file on disk is unaffected. Only the protected new file is downloaded.
No — all encryption runs locally in your browser. Your confidential documents never leave your device.
An unprotected PDF is accessible to anyone who gets a copy of the file — forwarded emails, shared drives, misaddressed attachments. A password means that even if the file ends up in the wrong hands, the contents remain locked.
This matters most for documents like medical records, financial statements, signed contracts, employment offers, tax returns, and identity documents — the types of files that cause real damage if they're read by the wrong person.
Our tool applies AES-256 encryption directly in your browser. The PDF never travels to any server. You encrypt it locally, download it, and share it knowing the content is protected.
User Password (Open Password) — Required to open and view the document. Without this password, the PDF appears as scrambled data. This is what you need when you want to restrict access entirely.
Owner Password (Permissions Password) — Allows the document to be opened by anyone, but restricts specific actions: printing, copying text, editing. Used when you want to share a document but prevent modification or extraction.
For most real-world use cases — emailing a contract, sending a payslip, sharing a report — the User Password is the right choice.
AES (Advanced Encryption Standard) is the same encryption algorithm used by banks and governments. At 256-bit key length, it's computationally infeasible to crack through brute force — the security is entirely dependent on the strength of the password you choose, not the algorithm.
The process inside your browser:
If someone opens the resulting PDF in any PDF reader (Adobe Acrobat, Chrome, Preview, Foxit), they'll see a password prompt. Entering the wrong password produces no content.
The encryption itself is unbreakable. The password is the only vulnerable point. Common weaknesses to avoid:
Weak: password, 1234, companyname2024, the client's name, any dictionary word
Strong: A phrase with mixed case, num...
Looking for a more detailed deep-dive and advanced tips?
Read Full Article on our BlogYour data never leaves this device. All processing is handled locally by JavaScript.
