Unfortunately for pedals 1, 2, 3 and 4 you can only assign:
1: Compressor or Wah
2: OD/Distortion or FX-1
3: Chorus or FX-2
4: Reverb/Delay or Sound on Sound
Using the "Pedal Assign" feature though you can assign multiple effects (e.g. Compressor Off, Distortion On, Octave On) to the expression pedal switch or the Bypass/Control pedal. I think you can plug in an additional switch pedal to use as well if you have one of those.
Okay so a little Pedal Assign guide... I'll use using the [i]CTL[/i] pedal to turn the compressor on and off as an example.
[b]Pedal Assign[/b][list=1]
[*]Press the [i]Pedal Assign[/i] button to the left of the [i]Tuner/Bypass[/i] button.
[*]Using the [i]Parameter[/i] buttons, find the settings for [i]Assign[/i] X. I'll use[i] Assign 1 [/i]as an example.
[*]Press [i]Pedal Assign[/i] to turn[i] Assign 1[/i] on.
[*]Press [i]Parameter Right[/i] to choose a [i]Target[/i]. Find [i]CL: On/Off[/i] for Compressor/Limiter: On/Off using the [i]Patch/Value [/i]wheel.
[*]Press [i]Parameter Right[/i] again and set [i]Min: Off[/i].
[*]Press[i] Parameter Right[/i] again and set [i]Max: On[/i].
[*]Press [i]Parameter Right [/i]again and set [i]Source[/i] as [i]CTL Pedal[/i]. (Set it to[i] EXP SW [/i]if you want to use the switch underneath the expression pedal. The [i]SUB [/i]settings are for external pedals.)
[*]Press [i]Parameter Right[/i] again and set [i]Mode: Toggle[/i] otherwise holding the pedal down will turn the compressor on and letting go will turn it off.
[*]Pressing[i] Parameter Right[/i] again shows you [i]Act. Range Lo [/i]and pressing it again shows [i]Act. Range Hi[/i]. You want [i]Lo[/i] to be 0 and [i]Hi[/i] to be the maximum allowed. (It should be like this by default).
[/list]
You can repeat the exact same process for each of the [i]Assign[/i] banks (1 - 8) so that one pedal turns multiple effects on and off.