PrintCentral Pro can connect directly to many Brother & Zebra mobile printers. e.g. Brother RJ-4040, PJ-673, RJ-2050, Zebra iMZ 220... Many of the Brother and Zebra mobile printers can connect via bluetooth too.
Not all bluetooth printers are compatible with the iPhone/iPad. Apple will need to approve the bluetooth connection so you need to check with your printer manufacturer to see if they have been approved by Apple.
If your bluetooth printer model can't connect to an iPhone/iPad then you can print from your device via the WePrint printer server on your Mac/PC. View

For connecting mobile bluetooth and wifi printers, check with your printer manufacturer documents to use the iPhone/iPad settings app to connect.
Generally this involves opening the device Settings app. Then open the Bluetooth settings and turn on the printer Bluetooth so you can add the printer as a device on your iPhone/iPad.

Once your printer is connected to your device, open PrintCentral Pro and open the Print screen. Tap on the "Choose" button to locate your mobile printer and select it.

Tap on the "Printer Options" button to choose your printer model and other settings like paper size and length.

Once selected, you can choose the driver with the tests in the setup screen: View