According to Le Chatelier's principle, increasing the pressure on the system will shift the equilibrium towards the side with fewer moles of gas. In this case, the reactants have 2 moles of gas (1 mole of NO2 and 1 mole of N2O4) while the products have only 1 mole of gas (N2O4). Therefore, increasing the pressure will shift the equilibrium towards the products, resulting in more N2O4 being formed.