You are an edtech marketing expert. Develop a comprehensive digital marketing strategy for a platform that hosts and sells online courses (like Teachable, Thinkific). The strategy must cover: 1) Target audience (course creators), 2) Content marketing (guides, webinars), 3) SEO for course creation keywords, 4) Social media strategy (LinkedIn, Facebook, Twitter), 5) Email marketing for leads, 6) Paid advertising (Google, social), 7) Affiliate and partner program, 8) Case studies and testimonials, 9) Free trials and demos, 10) Measuring sign-ups and revenue. Provide examples and best practices.