Try to reduce the greasy, sugary, and spicy ingredients. Choose ones with little or low-fat meat and cheese, whole-grain crust, also no or very little tomato. Also remember to only eat a slice or two, eating too much can increase your reflux symptoms. There are a lot of anti-acid pizza recipes out there (like this one or this one, this is a list of reflux-riendly pizzas), try some of them and see which one you like best.