That's interesting to hear. (Since this is the internet, let me be clear: that's not sarcasm)

Theoretically I really like the idea of reviewing code on paper.

But typically, if I'm trying to familiarize myself with a codebase, we're talking dozens of files. Usually I'm going through three, four, five levels of code to see how a request is served up, and then my search will fan out sideways into even more files as I attempt to see what other processes in the application might affect the data I'm concerned with.