Noteshelf now offers Apple Pencil Support for iPad Pro users. To get started, do the following:
1. For first time users, take off the cap of your Apple Pencil and plug it into the lightning connector on your iPad Pro.
(image from 9to5mac)
2. You'll see a Bluetooth Pairing Request. Tap on Pair.
3. That's it! If you want to disconnect the Apple Pencil, just go to your iPad Pro's Settings > Bluetooth then tap "Forget This Device." You won't be able to write using Apple Pencil on Noteshelf after this.