This study classifies hyperlinks or Complementary Digital Resources (CDR) present on the printed version of School Textbooks in terms of the a) Knowledge Genres or Curricular Genres to which they lead and b) the functions they play in the process of knowledge recontextualization. For this, a corpus constituted by 89 hyperlinks extracted from Language and Communication high school textbooks was analysed. The manual analysis was based on the following criteria: communicative purpose, modality, support of the discourse genres, and also the function these genres play in the pedagogical area. The results indicate that 55% of the CDR corresponds to Knowledge Genres (KG) such as Note or Biography, while the remaining 45%, to Curricular Genres (CG) such as Poems or Ted Talks. It was also observed that both KGs and CGs play, mainly, complementary functions.