The study investigates automated and controlled cognitive processes that occur when university students read multiple documents (MDs). We examined data of 401 students dealing with two MD sets in a digital environment. Performance was assessed through several comprehension questions. Recorded log data gave indications about students' time allocation, corroboration, and sourcing. Independent measures were used for reading speed to tap the effects of automatic processing and for working memory and single-text reading comprehension to tap effects of controlled processing, with working memory considered the mental capacity for performing controlled processing. We found that faster readers completed the MD tasks faster and showed more corroboration behavior. At the same time, students skilled in comprehension allocated more time to processing MD tasks and were more likely to show MD-specific behaviors of corroboration and sourcing. Students' success in MD tasks was predicted by reading speed and working memory, with the effect of working memory being mediated by single-text comprehension. Behavioral indicators contributed independently in predicting students' MD comprehension. Results suggest that reading MDs resembles a problem-solving situation where students need to engage in controlled, non-routine processing to build up a comprehensive representation of MDs and benefit from highly automated, lower-level reading processes.