Most wireless foot pedals work by emulating a computer keyboard. When a computer keyboard is connected to an iOS device, it automatically disables the on-screen keyboard. Most foot pedals have a feature which will "eject" this keyboard, allowing the on-screen keyboard to reappear.
If you have an AirTurn PED, press the keyboard button in the upper right corner of the button.
If you have an AirTurn DUO or QUAD, or a newer BT-200 series pedal, press the power button momentarily on the top of the module.
If you have an AirTurn BT-105, momentarily press the red button on the back of the module.
In you have a PageFlip pedal, press the current mode (CM) button, which lies next to the blinking light, to hide/eject the virtual keyboard (Firefly V1+ and Cicada V4+ pedals only)
For iRig Blueboards, simply press and hold in the left pedal for 3 seconds.
This will allow you to use both the foot pedal and then on-screen keyboard at the same time for the length of the session. You will need to repeat these steps each time the foot pedal is connected to your device.