As far as I can glean, there are three ways that democracy needs knowledge:
1. If citizens are to rule themselves, they must be competent to do so. This requires knowledge. And this is why we have universal education (this is Dewey and many others)
2. What makes democracy democracy is the diversity of knowledges that inform self-rule. Society thus needs to encourage thinkers as well as knowers. Dissent is important to democratic processes and it is enabled by this diversity of knowledges (Habermas and lots more)
3. Not every member of society can know everything there is to know, so democracy needs to be able to draw on experts (Dahl). This is linked to Plato's Philosopher Kings - rule is enabled by knowledge see earlier post. When we can print and distribute it easily, it functions nicely as a shared resource (Dewey). But after the Second World War, experts (not just their knowledge) were also seen (by Keith Murray) as a mechanism to prevent the collapse of democracy into totalitarianism.