Perhaps this is a bit basic, but I recommend finding where your target market reside and marketing to them there. If you are writing a course about topic X, then find where people who are interested in topic X are located and hit them there.
Amazon has an interesting print on demand option which may be a decent option for print and distribution, but not for marketing. You would just point people to your Amazon item page and let them buy from Amazon. There are of course other print on demand options.