Domain knowledge is mainly communicated to learners via un-assessed content such as text. Lack of effective support in reading activity of this type of resources, induces students misconceptions while increasing their cognitive load, leading to their demotivation. In this paper, we present the Learning by knowledge Construction approach (LKC). This system provides full student support for knowledge acquisition in reading activity. Aspects such as document annotation, external representations and argumentation are all taken into account. We describe an ITS architecture that implements this approach and give details on the authoring and student learning environments.