If you need help with Natural Docs, in most cases the best thing to do is to post to the Reddit forum. You'll get help from the community, and Natural Docs' author monitors it as well.
If you need to send code samples or other things you don't want to post publicly, you can also e-mail Natural Docs' author directly at gregv[xxx]alure @ natural[xxx]docs.org.
If you're a business and require a commercial support contract please contact Greg Valure.
If you need to report a bug and are comfortable with issue trackers, you can use Natural Docs' one on GitHub.