Protect PDF
Lock a PDF with AES-256 encryption and decide what readers are allowed to do with it. The password and the file stay in your browser, they are never uploaded to a server.
Add your PDF
PDF onlyDrop a PDF here or click to browse
Best for files under 50 MB
Result
Add a PDF to startYour protected PDF will appear here
The original file is untouched. Only the downloaded copy carries the password.
How to protect a PDF with a password
Add your PDF
Drop in the file you want to lock. It is read locally in the browser, nothing is uploaded.
Set the password and permissions
Choose an open password, then decide whether printing, copying and editing are allowed.
Download the protected PDF
The file is encrypted with AES-256 in your browser and is ready to download.
Why use Aihangsoft Protect PDF
AES-256 encryption
The strongest standard PDF supports, applied by the same engine that authors use to build the format.
Your password stays local
It is used inside the page to build the encrypted file and never travels over the network.
Free, no limits
No sign-up, no page limits and no watermark added to your document.
Two passwords, two jobs
Open password
Required before the document can be displayed at all. This is the setting that genuinely keeps a file private, because the content itself is encrypted.
Use case: contracts, payslips, medical recordsOwner password
A second, separate password for whoever administers the document. It lets you change permissions later without handing out the reading password.
Use case: documents you may need to unlock againPermission controls
Allow or block printing, copying text and images, and editing the document. Most readers respect these flags and grey out the matching commands.
Use case: sharing a draft that should not be reusedYour original stays untouched
The tool reads your file, writes a new encrypted copy and leaves the source alone. Nothing is modified in place and nothing is stored.
Use case: keeping an unprotected master copy