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 - GemBox
Hi,
This feature request has been implemented and is available in the latest versions of GemBox.Document.
Regards,
Mario