If you look at various calendar programs (perhaps even the one on your iPhone) they have "import" functions that let you put data in to the calendar without retyping it. If you mean PDF as in just a document with a roster in it, it's probably not in a form that you can import in that way - you need a more program-friendly format (iCal, Outlook CSV) to do it easily. A PDF is written for reading by people first, it's not designed to be fed in to another program. (Yes, there may be exceptions, but I never seen any, and without more details I have no reason to believe this is one of them.)
Are you currently synchronising your iPhone calendar with your computer e.g. Outlook, Google Calendar, anything like that? That is what I would do in your shoes - get the roster in to a calendar on the computer somehow, then sync it to the iPhone. It's easier to work on a computer, and syncing serves to back your calendar up, in case something goes wrong. Apple has its
MobileMe service for Mac users, which costs money (after a free trial), but you can do similar things with
Google Calendar Sync for iPhone at no cost. (If you have a Gmail account, you already have a Google Calendar option.)
I already do something similar: I sync the calendar on my Windows Mobile phone with Google Calendar over the Internet. This means that I can enter appointments on either phone or computer, and they get replicated across when I run a sync operation. If someone sent me a roster in the right calendar format (iCal or CSV) I could import it in a few seconds, then sync it across in a minute.
So I don't have a simple solution to offer, since I don't know what you're currently doing with your iPhone calendar, or what's in the PDF. As a minimum, if your calendar is important to your work, you should be backing it up or syncing it. If they can't give you anything suitable for importing in to a calendar program, you may have to re-enter the roster, but that's not such a big deal if you can do it on a big computer screen, rather than the little iPhone screen, and sync it across.