There may not be much information, but there is this:
The shield's pins, divided by channel are shown in the table below:
Function pins per Ch. A pins per Ch. B
Direction D12 D13
PWM D3 D11
Brake D9 D8
Current Sensing A0 A1
If you don't need the Brake and the Current Sensing and you also need more pins for your application you can disable this features by cutting the respective jumpers on the back side of the shield.
The additional sockets on the shield are described as follow:
Screw terminal to connect the motors and their power supply.
2 TinkerKit connectors for two Analog Inputs (in white), connected to A2 and A3.
2 TinkerKit connectors for two Aanlog Outputs (in orange in the middle), connected to PWM outputs on pins D5 and D6.
2 TinkerKit connectors for the TWI interface (in white with 4 pins), one for input and the other one for output.
Which tells you the pins it uses, from that, you can figure out whether the pins you want are available.
I think it uses different pins than the AFMotor library.