How to split word document by paragraph/headings in Openxml SDK?

I need to split a word document by paragraph.I have already splitted by sections.

Any help would be appreciated.

DocumentBuilder in the PowerTools for Open XML should do what you want. There is also a blog post and screen-cast about it from Eric White.

Is that what you used to split by section?

DocumentBuilder handles a lot of issues that you might miss in simpler documents (styles, fonts, comments, footnotes, etc.).