Some pie dough recipes call for a tablespoon or two of sugar. I personally prefer to omit it, which allows me to make either sweet or savory pies with the resulting crust. That said, you are welcome to add a bit of granulated sugar with the flour. Another option to increase the sweetness of the pie dough is to do a simple egg wash or milk wash on the edges of the dough prior to baking. Once the milk wash is on, you can sprinkle plain granulated sugar or turbinado sugar prior to baking to add sparkle and crunch.