Protect PDF
Add password protection to your PDF documents to prevent unauthorized access.
Privacy-first
Files never leave your device
Lightning fast
Instant protection
Secure
Password protection
Password Protection
Choose a strong password with at least 4 characters
Note: Protection runs locally in your browser using AES-256. Keep this password safe—we can't recover it for you.
Owner password matches the user password for compatibility. Use the Unlock tool later to remove protection.
Drop PDF here
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Protect PDF — Frequently Asked Questions
What encryption does this tool use?
FormatFuse uses qpdf with 256-bit AES encryption, the strongest algorithm defined by the PDF specification. This is the same level most corporate document systems apply to confidential files and is considered secure for routine sharing of sensitive documents.
Is a password-protected PDF actually secure?
AES-256 PDF encryption is strong against brute-force attacks when the password itself is strong. Short or dictionary passwords can still be guessed. Choose a long, random passphrase for anything you care about, and share the password through a different channel than the PDF itself.
Will the protected PDF open in Adobe Reader, Preview, and mobile apps?
Yes. The output follows the standard PDF encryption format, so Adobe Acrobat, Adobe Reader, Apple Preview, Chrome, Edge, Firefox, and the default iOS and Android PDF viewers all prompt for the password and open the file normally once it is entered.
Does FormatFuse see or store my password?
No. Encryption runs locally in your browser through a Web Worker running qpdf-wasm. The password is used to derive the encryption key and is discarded when the tab is closed. Nothing is transmitted and nothing is logged on our side.
Can I remove the password later?
Yes. Use our Unlock PDF tool with the password you set, and it will write out an unencrypted copy. Without the password there is no way to remove the protection — qpdf does not crack unknown passwords.
What encryption does this tool use?
FormatFuse uses qpdf with 256-bit AES encryption, the strongest algorithm defined by the PDF specification. This is the same level most corporate document systems apply to confidential files and is considered secure for routine sharing of sensitive documents.
Is a password-protected PDF actually secure?
AES-256 PDF encryption is strong against brute-force attacks when the password itself is strong. Short or dictionary passwords can still be guessed. Choose a long, random passphrase for anything you care about, and share the password through a different channel than the PDF itself.
Will the protected PDF open in Adobe Reader, Preview, and mobile apps?
Yes. The output follows the standard PDF encryption format, so Adobe Acrobat, Adobe Reader, Apple Preview, Chrome, Edge, Firefox, and the default iOS and Android PDF viewers all prompt for the password and open the file normally once it is entered.
Does FormatFuse see or store my password?
No. Encryption runs locally in your browser through a Web Worker running qpdf-wasm. The password is used to derive the encryption key and is discarded when the tab is closed. Nothing is transmitted and nothing is logged on our side.
Can I remove the password later?
Yes. Use our Unlock PDF tool with the password you set, and it will write out an unencrypted copy. Without the password there is no way to remove the protection — qpdf does not crack unknown passwords.