You can encrypt, add a certificate or a password to a PDF document and control access to your file. We’re going to show you how to password protect a PDF using Adobe Acrobat and Microsoft Word. If you’re more interested in making changes to your PDF, we have a simple guide on the easiest ways to edit a PDF too. Thankfully, PDFs have built-in support for password-protected encryption, unlike Microsoft Word. Whether you’re using Windows or macOS, there are several ways you can use to password protect a PDF document.