A book titled PDF Explained has been published by O'Reilly Media in December 2011. The author is John Whitington, who is the founder of Coherent Graphics Ltd, and "the author of one of the few complete PDF implementations, CamlPDF, which implements the PDF file format from the bit level up".
I had come across CamlPDF (which, as the name implies, is a PDF software product written in Caml, specifically, in the OCaml language) and its set of command-line PDF tools, a while ago (and may have tweeted or blogged about it then), but got to know about this book only today. Even though newer technologies such as EPUB are picking up (EPUB3 has been released), PDF has been and still is in very widespread use worldwide, and is not
likely to go away anytime soon; plus, its goals are not exactly the same as those of EPUB, so EPUB is not a complete replacement for PDF. So this book may be worth checking out for those who are or wish to be involved in PDF processing at a more than casual level.
Coherent Graphics develops command line PDF tools for Windows, Mac OS X, and Unix, and the Proview PDF Editor for Mac OS X.
- Vasudev Ram - Dancing Bison Enterprises