There are two ways that you can set a default app for opening PDF files. You can do it via "Right Click" or 'Device Settings'
Right click (or tap and hold) on a PDF file and select 'Open With' and then 'Choose Default Program'.
Ensure the option at the top 'Use this app for all .pdf files' remains ticked, and select Drawboard PDF from the list provided.
The selected document should now open in Drawboard PDF.
- Navigate to Device Settings > Apps > Default Apps OR press Win Key + type "file type"
- Near the bottom of the screen, tap 'Choose default apps by file type'.
- Swipe through the list until you reach '.pdf' and then tap the plus button on the right. If there is already a default app for '.pdf' then the plus button will have been replaced with that apps name and icon; tap that instead.
Swipe through the list that is shown until you find 'Drawboard PDF', tap on the app's name or icon and you are done!