Thinking of offering my girlfriend a Nexus 7 or iPad Mini. How is the PDF reading experience on the mini?

Did the same post on Reddit but on the Android side of things

My girlfriend is a Med Student and she already has a degree on Nutrition and Dietetics. She does lots of research and reads lots of scientific papers, so my question is, how comfortable is to read a scientific paper PDF in portrait mode without frequent zoom ins and zoom outs.

With a Nexus 7 it seems clearly not enough in Portrait mode, it works well in Landscape, but for two columns articles, its very sub-optimal.

How does it fare on the Apple side?