In large bowl with mixer at low speed, beat margarine or butter, shortening, and 1 cup sugar until blended.
Increase speed to high; beat until light and fluffy, about 5 minutes.
At low speed, add eggs, 1 at a time, and vanilla, and beat until well mixed.
Gradually add baking powder, baking soda, and 3 cups flour and beat until well blended.
With wooden spoon, stir in remaining 1 cup flour until soft dough forms.
If necessary, add additional flour (up to 1/2 cup) until dough is easy to handle.
Preheat oven to 350°F.
Divide dough into 4 equal pieces.
On lightly floured surface, shape each piece of dough into an 8 inch long log.
Place 2 logs, about 4 inches apart, on each of 2 ungreased large cookie sheets.
Flatten each log to 2 1/2 inches wide.
Place cookie sheets on 2 oven racks and bake 20 minutes or until lightly browned and toothpick inserted in center comes out clean, rotating cookie sheets between racks halfway through baking.
In pie plate, mix cinnamon with remaining 1/2 cup sugar.
Remove cookie sheets from oven.
Transfer hot loaves (during baking, logs will spread and become loaves) to cutting board; with serrated knife, cut diagonally into 1/2 inch thick slices.
Coat slices with cinnamon sugar.
Return slices, cut side down, to same cookie sheets.
Bake slices 15 minutes.
Turn slices over and return to oven, rotating cookie sheets between upper and lower racks, and bake 15 minutes longer or until golden.
Remove cookies to wire racks to cool.