There is no conversion. A calendar in Word can be in
any format - a table, text, Mayan symbols, well, you get the idea. For a conversion utility to work well, format must be constrained. So, for example, going from Outlook's or Thunderbird's Calendar to iCal is doable. Going from Word, a free-form text editor, to iCal offers no standard. A pdf has the same issue.
If you want an idea of what I mean, select a calendar in iCal and choose File menu > Export. Then, secondary-click the resulting .ics file and open it in Word (or TextEdit). That's a standard format. You may not be able to read it easily, but calendering software can.
Basically, you're stuck manually entering the information in to iCal.
You could always ask your professors to provide .ics files with the data. For example, my wife (a professor) distributes a Word document schedule for the lectures. But, she
could export the class calendar from iCal and distribute that, if anyone asked.