When using all purpose flour do you need to add baking powder and soda?

It depends on the recipe. All purpose flour is a blend of hard and soft wheat flours, and it typically already contains some baking powder and baking soda. However, some recipes may call for additional baking powder or baking soda to achieve the desired rise. If a recipe does not specify, you can usually add 1 teaspoon of baking powder and 1/2 teaspoon of baking soda per cup of all purpose flour.