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Protect your PDF with strong password encryption.
Drag and drop your PDF here, or click to browse
Free online PDF password protection
Protect sensitive PDFs from unauthorized access. Add a password, restrict copying and printing, and share your files with confidence.
Locks your PDF with a password so it cannot be opened without permission.
Prevent copying, editing, or printing your document by unauthorized users.
Your file is processed in your browser and never stored or shared.
Drag and drop or browse for the PDF you want to lock.
Enter a strong password to encrypt the document.
Get your protected PDF instantly and share it safely.
Free online PDF password protection
Password-protecting a PDF is one of the fastest ways to keep private information safe. Whether it's a contract, invoice, offer letter, or personal document, adding a password ensures that only people with the correct password can open it.
ModifyPDF lets you lock any PDF right from your browser — no signup, no software installation, and no waiting on server queues.
Control what others can do
A locked PDF is more than just password-protected. You can also restrict what someone is allowed to do with the file even after they open it — such as blocking copy, edit, or print actions.
This is useful for contracts, exams, reports, and any document where the content should stay exactly as delivered.
Perfect for sensitive documents
Documents often contain private information — bank details, business terms, medical records, legal papers, or client data. Sending them unprotected over email or messaging apps puts that information at risk.
By adding a password, you make sure that only the intended recipient can open the file, even if the document is forwarded, downloaded, or intercepted.
Private and secure
Encryption happens directly in your browser using local processing. The tool does not upload the original PDF to a server, which makes it a safer option for sensitive files compared to traditional online tools.
There is no account required and no watermark added. Just upload, set your password, and download the locked PDF.
Best practices
Popular use cases
Protect agreements, NDAs, and proposals before sending
Keep legal papers safe when sharing with clients
Protect IDs, medical records, and personal reports
Secure offer letters, payslips, and internal reports
Questions and answers
We use standard strong encryption. Once locked, the PDF cannot be opened, printed, or modified without the correct password.
No. The password is cryptographically embedded into the file. If you forget it, the file cannot be recovered, so please keep your password safe.
Your file is processed in your browser and is never stored or shared.
Yes. ModifyPDF is fully optimized for iOS and Android, so you can lock PDFs directly from your mobile browser.
You can securely lock PDF files up to 100 MB for free.
Yes. If you know the password, you can remove protection using an unlock tool. Without the password, the PDF cannot be unlocked.