To score prospects separately based on their interactions with different product lines in Pardot, the best approach is to assign a scoring category to each product line folder. Scoring categories allow administrators to segment prospect scoring based on interactions with specific types of content, aligning with different business units, products, or campaigns. By assigning a distinct scoring category to each folder associated with a product line, an administrator can precisely track and score prospect engagement relative to each product line. This tailored scoring provides deeper insights into prospect interests and can better inform targeted marketing strategies.