Generate a detailed outline for a 500-word article on optimizing trial-to-paid conversion flows for SaaS products.  The article should focus on practical strategies and actionable tactics, avoiding generic advice.  Specifically, the article should cover at least three distinct stages of the trial process: onboarding, engagement, and the conversion itself.  For each stage, provide specific examples of effective messaging, in-app guidance, and feature highlights to encourage users to upgrade.  The article should also discuss the importance of A/B testing different elements of the conversion flow, including email sequences, in-app notifications, and pricing options.  Finally, include a section on identifying and addressing common pain points that prevent users from converting, with actionable solutions. The target audience is SaaS founders and marketing professionals.  The output should be structured as a numbered list of sections, with subsections detailing specific tactics and examples for each stage.  Successful completion will be measured by the clarity, actionability, and specificity of the suggested strategies, as well as the inclusion of relevant examples and A/B testing considerations.  The focus should be on measurable improvements in trial-to-paid conversion rates.