Combine flour, baking powder, soda, and salt; stir well. Cut in shortening with a pastry blender until mixture resembles coarse meal. Gradually add buttermilk, stirring until dry ingredients are moistened.
Turn dough out onto a lightly floured surface, and knead 10 to 12 times. Roll dough to 1/2-inch thickness; cut with a 2-inch biscuit cutter. Place biscuits on an ungreased baking sheet. Bake at 400° for 10 minutes or until lightly browned.