Sift together the flour, baking powder, baking soda and salt; set aside. In a large bowl, cream together the shortening and sugar until smooth. Beat in the eggs one at a time then stir in the vanilla and sour cream. Gradually mix in the sifted ingredients until just blended. Cover or wrap dough and chill overnight.
Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets. On a lightly floured surface, roll the dough out to 1/4 inch in thickness. Cut into desired shapes with cookie cutters. Place cookies 1 1/2 inches apart onto cookie sheets.
Bake for 10 to 12 minutes in the preheated oven, until edges are lightly browned. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.
