Protect PDF with a password
Payslips, bank statements, contracts and medical reports are often emailed as plain PDFs that anyone can open. DMI's Protect PDF tool adds a password so only people you share it with can read the file. It uses AES-256, the strongest encryption in the PDF standard, which Adobe Acrobat, Chrome, Edge, Firefox, macOS Preview and phone PDF viewers all open. You can also choose what readers may do once the file is open: print it, copy its text, edit pages, add comments or fill in forms, and set a separate owner password that lets you change those permissions later. The encryption engine is open-source Rust code compiled to WebAssembly and runs entirely in your browser, so your document and your password are never uploaded to a server.
How it works
- Add the PDF you want to protect.
- Type the password twice, and optionally set an owner password and permissions.
- Click Protect PDF to download the encrypted copy.
Frequently asked questions
Is protecting a PDF free?
Yes, adding a password to a PDF with DMI is completely free, with no signup, no watermark and no limit on how many files you protect.
Are my files and passwords private?
Yes. Encryption happens entirely in your browser, so neither the PDF nor the password is ever uploaded to a server. We log usage metadata, including your IP address, tool name, filename, and file size, for up to 12 months to help prevent abuse, but never the file contents or passwords.
What if I forget the password?
AES-256 cannot be broken in practice, so a forgotten password cannot be recovered by us or anyone else. Keep the original unprotected file, or store the password in a password manager, before you share the protected copy.