Password protect a PDF
Add a password to a PDF so it cannot be opened without it.
How it works
- Drag and drop your PDF files below.
- Choose a password and confirm it — every file gets the same one.
- Click Lock PDF to start.
What this tool does to your file
Locking a PDF here applies AES-256 encryption, the strongest the PDF format defines, and the password you choose is set as both the open password and the permissions password — leaving the second one empty is a common shortcut that lets any reader open the document with full rights, so this tool does not take it. Everything else about the document is left alone: pages, text, links, form fields and page sizes come back exactly as they went in, because encryption wraps a document rather than rebuilding it. You can lock several files at once and they all take the same password; one file comes back as a PDF and several come back in the archive format you pick. Choose the password carefully — there is no recovery, and neither we nor anyone else can open the file without it, which is the entire point. Your password is sent once with the job, is never included in what the server sends back, and is deleted from the job record as soon as the job finishes. A file that is already password-protected is refused rather than encrypted twice; unlock it first if you want to change its password.
What happens to your files
- No account needed — Every tool works as a guest. Signing in raises the limits and keeps your files together, but nothing asks you to register before you get a result.
- It runs in your browser — There is nothing to install and nothing to keep up to date. Files travel to our servers over an encrypted connection, and come back the same way.
- Your files stay yours — Files and results stay in your account until you delete them. Files from a guest session that is never linked to an account are removed automatically after a period of inactivity.
- Size limits, stated up front — Up to 10 MB per file as a guest, and up to 25 MB signed in. You see the limit before you upload, not after.