The PC1X, like many performance controllers uses thge terms Programs and Setups instead of patches and presets because it's not a synth which makes the manual a hard read for the uninformed but to get what you want you are going to have to read it real good. Theres a section on editing setups and other info in the manual about using MIDI controllers. You just have to read it over a few times and become familiar as it is a bit disconnected but it does give you hints and tell you you should already be familiar with blah blah blah in which case you just have to go read that section anyhow.
The setups section describes how to setup a dual switch pedal in which one pedal is a sustain and the other is programmable. Esentially if you want to do an intro with piano, go to strings etc. for the verse and chorus and a synth or whatever for the solo you set up these three SETUPS and save them in the user bank, the first 127 of which are already in use and theres three others which are in use by the keyboard like a blank setup (sort of like an initial patch) then one with no voice setup but basic controller assignments and anothr I dont remember.
ANY how then you have to assign the pedal to SETUP INCREMENT which is apparently ALL the way down at the bottom of the menu then you can use the pedal to skip through the setups but only in one direction. this seems pretty nutty to me.
A much easier way I think would be to get a MIDI foot controller like a guitarist would use then make and save your setups patches or whatnot to whatever slot then you can assign the MIDI pedals to go directly to that specific sound.
The Manual literally has a single line that refers to the fact that you can do this, right under the paragraph of explanation about the previous terrible method.
The PC1X has a built in app called MIDIscope which will read out any midi activity on the display, so you can just get your foot controller, plug it in and read off what CC commands result from hitting the foot switches. Then program those eight or so commands to switch the keyboard to setups you've saved in the 130 or so user slots and there you go. you gotta read the manual for all the menus as there are a lot.
a behringer foot controller has 12 foot swithes and two expression pedals any of which can be assigned to anything on the pc1X and you can get one for about a hundred bucks. I'm going to build one out of a korg nanokontrol I bought for 7 bucks.
Tell your keyboardist to try controlling the arpeggiator with key pressure, its great fun.