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Protect a PDF with a password (Mac, Windows, CLI)

Add an open password to contracts, invoices, and other PDFs — and understand the limits of the editing password.

By FileHint editorial teamSupervised by Netwiz LLCEditorial policy

Two kinds of password

  • User password: required to open the document.
  • Owner password: restricts editing or printing. Trivial to strip — don't rely on it for confidentiality.

Mac (Preview.app)

  1. Open the PDF in Preview.
  2. File > Export.
  3. Check Encrypt and enter a password.

Windows (Word save-as PDF)

  1. Save As > PDF.
  2. Options > Encrypt the document with a password.
  3. Choose a strong password.

CLI (qpdf)

qpdf --encrypt USER OWNER 256 -- input.pdf output.pdf

Operational tips

  • Send the password via a different channel (phone, SMS).
  • Encryption isn't a substitute for treating the document as confidential — ask the recipient to delete after use.

Related extensions

References