Corn flour is exactly what it sounds like: flour made from corn. Since corn is not Paleo, neither is corn flour.
Paleo and Grains
Although it’s gluten-free, corn is still a grain (not a vegetable), so it can’t be included on the Paleo menu. It’s very high in carbohydrates and low in nutrients.
Paleo and Sugar
There’s a reason they make it into corn syrup: because there’s so much sugar already present in corn. Even if you’re eating whole corn kernels straight off the cob, you’re still getting a load of sugar. Since living a Paleo lifestyle is about eating nutrient-dense foods and sometimes that includes pretty low-carb (and very low sugar), corn flour loses on both counts.