Hrm, the PDF from your site loads on my iPhone, but only partially -- definitely not what I would call functional. However, we will probably focus on improving the 2.3.x PDF view function (which has been changed drastically from what you see in your 2.2.4 version of OJS). PDFs from 2.3.x versions of OJS seem to load fine for me in my phone, and I'll definitely ask other PKPers with iPads to confirm one way or the other.
If you aren't able to upgrade to 2.3.x in the near future, you may want to investigate some sort of browser-detection function that displays PDFs differently for mobile devices. If/when we look into this for 2.3.x, I'll definitely try and keep you posted, and can possibly help with backporting.