Pagination

One of the biggest drawbacks to using a book on an iPad in a class is going to be pagination. Right now, if I want to draw students attention to something, I can tell them what page it is on. While there are pages on the iPad, they change based on font size and orientation. The book I read is 309 pages. However, that is in the orientation and font size I am in. If I turn the iPad sideways, it suddenly becomes 621 pages. Turn it back and drop the font down two sizes, and it is suddenly 193 pages. I can never say turn to page 244. I wonder if it is possible to get it sized just right so it matches the original. Alternatively, if everyone is using an iPad, I could get everyone to orient the iPad and set the font size just like mine. I wish it had some way of referring to a common page number, preferably from the original.