I wish that I could give you an absolute, definitive answer to this question. The problem is that Peter Pan is an old book. On top of that, it is a very popular book. Together that means the book has been through many different print versions. Without knowing exactly which version/edition the question is asking about, the best that I can do is offer specifics about editions that I have or can currently buy.
The original J. M. Barrie version included illustrations and was a hardcover. It was 240 pages in length.
The 1987 Centennial Edition (paperback) version is 208 pages in length, but that includes an afterward written by Alison Lurie.
The current 2014 paperback edition has an extremely low page count. It has 94 pages, which sounds incredibly short, but page counts can differ a lot as font sizes and font types are changed from version to version.
Of course, if you don't mind altered and annotated editions to give readers the shortest possible story, then I recommend the 2007 Walt Disney's Peter Pan Little Golden Book edition. It's 24 pages long . . . with lots of illustrations. My four year old loves it.