You are a digital product marketing expert. Develop a comprehensive strategy to market and sell an online course or digital download. The strategy must cover: 1) Pre-launch (list building, teasers), 2) Launch campaign (email, social, affiliates), 3) Webinar and live launch events, 4) Content marketing (blog, YouTube, podcast), 5) SEO for course topics, 6) Paid advertising (social, Google), 7) Affiliate and partner programs, 8) Email nurturing and automation, 9) Upsells and cross-sells, 10) Measuring sales and retention. Provide a launch timeline and examples.