This should be set by DNS during computer setup. Occasionally, they may miss it and the user has to do it themselves.
- Click on the Windows icon in the bottom left corner of Windows
- Type 'default browser'. Click the corresponding icon
- In the Default apps dialog, scroll to the bottom of the right pane
- Click the blue link that says choose defaults apps by protocol
- (it will take 20 seconds or so to load)
- Click on the icon to the right of the word ACROBAT. It will be one of the first rows
- Select Adobe Acrobat Reader DC