Protect PDF
Add or remove a password with AES encryption and permission controls - 100% in your browser.
Drop a PDF here
or click to browse
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About Protect PDF
Password protecting a PDF is what you do before sending a tax return, a medical report, a contract or anything else that should only open for one person.
There is an awkwardness in how this is normally done online. Protecting a document means uploading the unencrypted version to a server and typing the password into someone else's form, so for a moment the very thing you are trying to secure sits on infrastructure you do not control, alongside the key to it.
KuroPDF encrypts using a WebAssembly build of qpdf, the same library behind many desktop and server PDF tools. The document and the password both stay on your device, and the encrypted file is written locally. You can also remove a password you already know, which is useful before merging or editing, since most tools cannot read an encrypted file.
Choose AES-256 unless you have a specific reason not to. AES-128 exists for compatibility with older readers, and RC4-40 is present only because some legacy systems still demand it and should not be treated as secure. Permissions for printing, copying and editing can be set separately from the open password, though it is worth knowing that permissions are advisory: they are respected by well behaved readers and ignored by determined ones. The open password is the part that provides real protection.
How to protect pdf
- Load the PDF
Drop in the document you want to lock.
- Set a password and level
Choose AES-256 unless an old reader forces otherwise, and set permissions if you need them.
- Encrypt and download
The encrypted file is produced in your browser and saved to your device.
Related tasks
Guides for the specific jobs people bring to this tool. Each one opens the same tool with the right settings.
Frequently asked questions
How strong is the encryption?
AES-256 is the current standard and is used by governments and financial institutions. Its practical strength depends on your password, since a short or common one can be guessed regardless of the cipher.
What happens to my file after I protect it?
Nothing, because it never left your device. There is no server copy, no retention window and no policy to trust. Other services have to answer this question by describing their deletion schedule.
Can I remove a password?
Yes, if you know the current one. This tool decrypts as well as encrypts, which is often needed before merging or editing, since most tools cannot open an encrypted file.
Can I stop someone printing or copying?
You can set those permissions, but be realistic about them. Permission flags are honoured by well behaved readers and ignored by others. Only the open password genuinely restricts access.
How do I send a protected PDF safely?
Send the password by a different channel from the file. Emailing both together defeats the purpose, since anyone reading the message has each half.