How to Password Protect a PDF for Free (No Software)

Sending an invoice, a payslip, or a signed agreement by email? Anyone who intercepts that message — or simply receives a misdirected copy — can open the attachment. Password-protecting the PDF means only someone with the password can read it, and you do not need expensive software like Adobe Acrobat to do it.

PdfWill encrypts PDFs using AES-256, the same standard trusted for banking and government documents. Crucially, the encryption happens entirely inside your browser using WebAssembly: the file and your password never travel to a server, so there is no chance of them being logged or leaked in transit.

Here is how to do it: open the Protect PDF tool, upload your document, type a strong password (at least 8 characters, mixing letters, numbers and symbols), confirm it, and click Protect. Download the encrypted file. From now on, anyone opening it — in any PDF reader — will be prompted for that password.

Two reminders. First, there is no 'forgot password' button for an encrypted PDF; if you lose the password, the file is unrecoverable, so store it in a password manager. Second, share the password through a different channel than the file itself — for example, send the PDF by email but the password by text message — so a single intercepted message can never expose both.