When you install PDF Reader for the first time, you will be seeing an unknown publisher warning from Microsoft Defender (Windows' built-in antivirus program). The message looks like this (using Surface Pro as an example):
To continue the installation, please follow the instructions: (Using Microsoft Surface Pro as an example):
1. Click “Run Anyway” to continue installation. You may need to click "More Info" if the button is hidden in the warning message.
Then click “Run Anyway” to continue the installation