Protect PDF
Secure sensitive PDF files with robust 128-bit & 256-bit AES encryption. Set owner and user passwords to prevent unauthorized viewing, printing, or copying.
Protect and Encrypt PDF Documents with High-Security Passwords
Financial disclosures, confidential employee payrolls, contracts, legal discovery packages, and proprietary design blueprints must never fall into the wrong hands. Our Free Online PDF Protection Tool equips you with bank-grade cryptographic controls to encrypt your PDF documents with custom passwords, locking out unauthorized readers permanently.
We implement industry-standard 128-bit and 256-bit AES encryption algorithms compliant with standard PDF specifications. Once protected, opening the document in Adobe Acrobat, Apple Preview, Google Chrome, or any standard PDF viewer requires typing your secret password. Without the password, the document's internal character streams remain completely indecipherable.
Your encryption password is processed in-memory and never logged, stored, or transmitted to any third party. Your files are protected by TLS 1.3 in transit and automatically deleted from our server cache within 60 minutes.
Guards document contents with cryptographic algorithms that cannot be brute-forced or bypassed by standard PDF reader utilities.
Encrypted documents prompt for password authentication seamlessly on Adobe Acrobat, Apple Preview, Foxit, Chrome, and iOS/Android readers.
Your password is never saved in databases, server logs, or caching systems. We have zero knowledge of your encryption keys.
Original and encrypted files are permanently erased from server storage within 60 minutes of completion.
How to Password Protect a PDF File
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1
Upload the PDF Select or drag your PDF document into the workspace above.
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2
Set Your Secret Password Enter a strong, secure password in the password field. Be sure to remember or store it safely.
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3
Encrypt and Download Click "Process Files" to encrypt the document and download the locked PDF immediately.
Frequently Asked Questions
What happens if I forget the password I set?
Because we use authentic cryptographic encryption and never store your password, the file cannot be decrypted without the password. Always keep a backup of your password in a password manager.
Does this prevent unauthorized printing and editing?
Yes. An encrypted PDF cannot be viewed, printed, altered, or have its text copied unless the reader unlocks it with the correct password.
Can I protect PDF files on my phone or Mac?
Yes! Our tool is 100% cloud-based and responsive. You can encrypt PDFs directly through Safari on iPhone, Chrome on Android, macOS, or Windows without downloading third-party software.
Is this service completely free?
Yes. Paperknife Solo does not charge fees, require accounts, or add watermarks to your secured files.