I just posted the recording of the webinar that I did today showing a Word 2007 Add-in that creates WPF Flow Documents (using the FlowDocument class):
Here's an example of where I've used it to create a FlowDocument of a Whitepaper.
Here's what it demonstrates:
If you want to download the source code, go to Popfly.ms and look for the WordFlowDocumentCreator project. Add me (MS-Synergist) as a friend while you're at it.
Here are links to all of my recorded webinars if you want to watch them as well.