With the UP-MP-WP merger approved, UP issued this map in 1983. It might be hard to tell from the PDF, but the cover and the map are printed on two different pieces of paper and glued together.
In years past, railroads would put advertising on the backs of their maps. Either because this map was issued in haste or because the railroads no longer had any passenger trains to advertise, the back of this map is blank. The PDF therefore only has one page.