Sometimes, even though you set the Default PDF application to be set to Power PDF when you were setting up the installation parameters in the customization kit, the default PDF application is not changed to Power PDF after installation. This can also happen when manually install the software or when you try to change the default PDF application from the General Options, and it can happen when you try to change the default application from the command line using the defaultviewer.exe utility. (see kb 17971 for more information on using the DefaultViewer utility)
This is a known issue with Windows 10 security preventing our application from setting itself as the default application for PDFs. The only solution in this case is to manually change this association in Windows.