Just remember, assigning a controller footswitch to toggle a  POD FX Block on/off is a two step exercise.

1)  Assign a footswitch within the HD Pro to toggle the effect on/off that you want to control.  Of course there is no physical footswitch on the HD Pro but you can still do it within HD Edit.  Details in the advanced manual or here --> http://line6.com/support/docs/DOC-2721

2)  Assign your midi controller pedal to send a Midi CC to toggle the required 'footswitch' on the HD Pro.   e.g. Midi cc 051 controlls FS1.  You can send any value within the cc  message  to the POD and the footswitch will toggle.