This study aimed to analyze the factors affecting multiple-document selection and use in a digital context. With content relevance and source credibility (i.e., author expertise) as within-subject factors, 16 documents of four categories were implemented in a digital context. In total, 450 high school students were sampled, and the documents of whose features were selected and used were examined using repeated-measures ANOVA and treating topic familiarity and epistemic beliefs for “cultural diversity” as between-subject factors allowed us to identify how multiple-document selection and use differed by individual differences. Participants paid more attention to content relevance than to author expertise. Participants with low prior knowledge selected more documents; however, when extracting information units from documents and using them in their own essays, participants with high prior knowledge showed more elaborated performance. Depending on the level of epistemic beliefs, more documents were selected and used by participants with naive beliefs.