A very readable "how to" book. It sets out to show how pdf files can be used, manipulated, altered, made intelligent etc. The book can be read in parts: read first the parts that relate to problems or uses you have.
Oh, and of course you need to get the software it describes to work. :)
It is crazy it seems the is such a little gem of a book, really powerful tools that enable you to do things using free software that costs £500 plus to do in adobe pro. Well worth a read, again as you come stuck with the world of pdfs.