Reading skills are essential to acquire technical and scientific knowledge. This is especially relevant in formal education and training contexts, as Adult Learning (AL) and Vocational Educational Training (VET), and in work contexts, such as when companies provide written instructions to their workers. People with low literacy skills are less able to acquire and maintain transversal and durable skills needed to stay apace with the changing job market and to lead meaningful and complete lives. However, promoting reading habits and skills in adults is quite challenging due to the lack of dedicated and/or adequate reading materials. Supporting the adoption of innovation in adult training, the iRead4Skills project aims to promote the development of reading skills through an innovative intelligent system that evaluates texts complexity and suggests reading materials adequate to the user reading level, which can also be used by trainers in the creation or adaptation of texts with the appropriate level of complexity for their individual students. The main target audience of the iRead4Skills project are, thus, low literacy skills adults, which include adult native speakers, integrated in a dynamic linguistic community, but also other second language (L2) speakers, not necessarily in L2 formal classes. To achieve the main goals of the project, we focused on three levels of complexity, defined according to relevant reference documents that cover adult skills (PIACC 2016, ANQEP 2021) and language proficiency levels (Common European Framework of Reference for languages (CEFR) 2020) and that explicitly describe reading skills.