There is a transfer desk right before the entrance to the ITI kiosks (my BP got ripped and I had to have a new one printed). I don't think you'll be able to use a boarding pass printed on letter paper at the ITI kiosks because they seem to only work with a "correctly sized" thick stock BP.

I think you'll be fine going to the transfer desk, handing them your passport and telling them you need your onward BP (luggage issues notwithstanding)