Unfortunately, the AirTurn Manager is only used to test the AirTurn Duo's functionality and change its configuration, so you need to find another App to actually view the music sheet PDF that we had downloaded.
At first we tried using the Musicnotes Sheet Music Player from the Apple App Store on the iPad.
We tried to import the PDF file that we had transferred using AirDrop to the Musicnotes Sheet Music Player App but you need to use iTunes to synchronize files.
Unfortunately, there was no way to open the PDF after the AirDrop transfer.
We then downloaded the piaScore App.
Here you can use Google Drive to easily transfer PDF's to be used by the piaScore App.
You can then pair with the AirTurn Duo through the Bluetooth settings menu of the Apple iPad Pro- 12.9". To start the Bluetooth pairing process, you just need to turn on the AirTurn Duo's power and it will automatically show up in the My Devices list. You can simply pair the devices together by selecting the AirTurn device in the My Devices list.
Initially,the AirTurn Duo apparently acts like a keyboard on the Apple iPad Pro- 12.9" which means that while it's paired, you won't be able to use the iPad's virtual keyboard. In order to get the virtual keyboard back, you need to press the AirTurn Duo's power button again which maintains the Bluetooth pairing so you can still turn the page by pressing the AirTurn Duo and make text notations on your PDF.