I see more people use the standard Word themes for styling their documents, since its so easy to use and looks good as well:
https://support.office.microsoft.com/en-us/article/Apply-themes-to-Word-documents-5b56d5ee-d2d4-4a01-ad3a-cc0abcf20f5f
However, Gembox doesn't (fully) support it.
Otherwise, it's a great product with an even more awesome price!
Official response
Mario at GemBox
Hi,
This feature request has been implemented and is available in the latest versions of GemBox.Document.
Regards,
Mario