The promise of digital libraries is an easy and rapid access to digital documents using information technology. However, in an educational context, helping the students access the right document is not sufficient. Systems must be able to help during the reading phase as well. We present the LEKC framework (learning by explicit knowledge construction) [K. Rouane, et al. (2000)] which aims to take advantage of the natural annotation activity to increase the reader's engagement with the document and enhance his understanding, by externalizing and making explicit some of the implicit knowledge construction processes taking place.