This study examined the factors of learning behaviors in digital-learning-material reader that predict university students' productive participation identified by social presence indicators in online collaborative learning. Data were collected from 76 first-year university students, including learning behaviors in digital learning-material readers, and frequency of each social presence indicator classified by coding discussion scripts with automated text classification. The results of the stepwise multiple regression analysis revealed that the learning behavior of drawing red markers, highlighting important content predicts social presence. Furthermore, the study's findings showed that different learning behaviors predict different social presence indicators, which are related to metacognition and critical thinking.