You probably can, because I looked up several recipes which gave you a choice as to the kind of fat to use. You can also use margarine, but if you use the "low-fat" butter or "low-fat" margarine, they have higher water contents, and you may need to decrease the amount of water used in the recipe.

The best suggestion is to try a recipe out with butter in place of the shortening -- just be sure it's very cold, for that's what creates the "flakiness" of the pie pastry.

I have also included another pie crust recipe from www.pierecipe.com which specifically allows for the substitution of different fats:

Pie Crust with Butter

INGREDIENTS:
1 cup cold, unsalted butter OR 1/2 cup cold unsalted butter and 1/2 cup shortening OR 1 cup cold, unsalted margarine
3 cups all-purpose flour
3 tablespoons white sugar
1/3 cup cold water (approx.)

DIRECTIONS:
1. Combine flour and sugar into the bowl of an electric mixer. Cut butter or margarine or butter and shortening into tablespoon pieces; add it to the flour and butter. Use the paddle beater to cut the butter and flour together. Alternatively, this can be done by hand with a pastry blender.

2. With the mixer on low speed , or while stirring the mixture with a fork, pour in the cold water. When the dough starts to clump, and before it turns into a ball, stop stirring.

3. Lightly knead dough in the bowl until it forms a ball. Divide dough into two parts. Flatten each part into a disk, and chill for about 30 minutes before rolling.