This study investigated the effects of author expertise and content relevance on Norwegian secondary school students' (n = 190) selection, processing, and use of multiple documents. Participants were presented with documents that pertained to more or less familiar topics, and received brief instructions that highlighted the importance of source credibility or content relevance, whereas those in a control group just received a general task instruction (to write a letter to the editor about their assigned topic). Results showed that content relevance had strong and nearly identical effects on students' selection, processing, and use of documents independently of whether the topic was more or less familiar, whereas they valued author expertise to a greater extent when the topic was less familiar. Moreover, content relevance had a strong effect on students' selection, processing, and use of documents independently of instructional condition, whereas brief instructions to focus on source credibility increased the value placed on author expertise when students selected, processed, and used documents for the less familiar topic. Theoretical and practical implications of the results are discussed.