In this paper, we analyze the interactions between personal information management (PIM) and professional knowledge of teachers. PIM is studied through operations of classificatory documentarization, that is, the classification, naming and indexing of resources (Zacklad et al., 2011). Teachers' professional knowledge relates to the subject matter content knowledge, pedagogical content knowledge and curricular content knowledge (Shulman, 2007). The interactions are analyzed in the context of optional course, called ‘Informatics and Digital Sciences’ and introduced at grade 12 (fall 2012). We conducted interviews with 5 teachers. We have complemented this collection of data with the observable products of the PIM: the files and bookmarks trees. The results show that the various operations of classificatory documentarization aim at first at a need for reinsurance of the knowledge. This need can concern the preparation of the courses or the activity in class. It is supported by one or several reference collections (Jones, 2007), by a classification allowing the reactivity in class and by always available personal media.