Lower the cognitive load
One of the challenges for a student trying to read a complex text in a second language is that they’re having to deal with the ideas in the text at the same time as the language. One way to get around this is to use simpler or more familiar ideas while keeping the language level high. That doesn’t mean dumbing down necessarily, but could involve choosing a text on a subject that students are likely to be familiar with, perhaps because it’s already been discussed in a previous lesson. In an EAP context, you could drop down an academic level, so if you’re writing for postgraduate students, choose introductory undergraduate texts and if you’re aiming at undergraduates, use end of high school texts (such as textbooks written for students doing the International Baccalaureate). In that way, you maintain the style and authenticity of the language, but lessen the cognitive load on the reader.
There are also plenty of techniques which can help students grasp the key ideas in a text more easily so as to free up mental space to deal with the language. Pictures, diagrams or infographics can all be added to aid comprehension. If a text contains a lot of detailed statistics, for example, a graph or an infographic can help to establish what’s going on. Then readers will already know more-or-less what to expect in terms of content and can focus on getting to grips with the details and the way they’re expressed.