To work with the PDF plugin of the DITA Open Toolkit, you will need a few tools.
You need to have the DITA Open Toolkit installed, of course. This book is written for the DITA Open Toolkit 1.8, which is the current stable release as of the publication of this book. There are three versions available for download: minimal, standard, and full. The full version installs not only the XSLT stylesheets and ANT build files, but also ANT, FOP, and some other tools you need. It’s really your best bet to be sure that you have a clean, fully-integrated installation that works out of the box.