Encrypt an Adobe Acrobat DC document with a VT Personal Digital Certificate (PDC) on Windows
When using Adobe products, you can only encrypt a PDF with Adobe Acrobat (the paid version). You cannot encrypt a PDF with Adobe Reader (the free version).
1. Install your PDC in the Windows certificate store per the KB article titled "How do I import a PDC into the Windows Certificate store?".
2. Use the information at https://helpx.adobe.com/acrobat/using/securing-pdfs-certificates.html in the section titled “Encrypt a PDF or PDF Portfolio with a certificate” to encrypt your document with a PDC.
To perform this on Mac OS, you must run Windows. See Installing Windows on macOS with VirtualBox, Boot Camp, or Parallels.