DocumentBuilder 2.0 is a much-improved version of the DocumentBuilder class that is part of PowerTools for Open XML. Using DocumentBuilder, you can split Open XML WordprocessingML documents apart, and merge and combine them in a variety of ways. DocumentBuilder deals with the many issues associated with interrelated markup in Open XML WordprocessingML.
This third screen-cast in this 3 part series explains how DocumentBuilder is data-driven so that it is more robust.
You can find a complete list of DocumentBuilder 2.0 content as well as links to download it in the DocumentBuilder Wiki Page on OpenXMLDeveloper.org.