I of course (like you) don't condone downloading copyrighted PDF books,
but (via Google search) see it's on 4Shared: here

That said, in the case of 'The Real Book fifth edition',
that edition of the book was produced with no royalties paid to the composers whose songs appear in that book,
so consequently, the actual book itself violates copyright laws and technically illegal.
Before the digital age, the paper bound version of the book was usually sold surreptitiously in local music stores,
often hidden behind the counter for customers who asked. Here's more interesting information & history on the 'original' "The Real Book".

Scott

A little colloquial “Fake Book” history: Back in the early ‘50’s, before “Fake Books” were sold surreptitiously in music stores, it was an exciting escapade to procure one. Here’s how we purchased our first “Fake Book”; we contacted a guy who knew guy, we were given a description of a car, then we were instructed to go to a busy side street in Philadelphia, find the car, and on the back seat, driver’s side, we would find “the package”. We put the money on the seat and took “the package”.
Ciao,
Jerry

Uncle Dave and Fran, this was pre-Benny