Here are the instructions on how to pair using SSP (Simple Secure Pairing):
After turning the printer's power switch on, press and hold the PAIR button on the rear interface of the printer for 5 seconds or more until the LED flashes green, and then release it. Pairing will be possible for 60 seconds from when the LED starts flashing green.
During this time, perform pairing from the iPad. Go to Settings > Bluetooth > turn the switch to on (switch should be green with the note underneath "Now discoverable as...")
After performing pairing, wait until the LED stops flashing green, or turn the printer off and back on again, to enable the connection. The device should now be listed under My Devices on the iPad.
The bluetooth printer is now paired with / connected to the iPad.