You need moisture for the pita bread to puff up in the oven. If your dough is too dry due to too much flour, the bread won’t puff up. Also, you want well-developed gluten in the dough. Make sure to knead the dough until it feels soft but stretchy. This allows the bread to stretch and rise in the oven. Finally, you don’t want the dough to be thick when you place it in the oven. Make sure to roll it thin and evenly. If the dough is too thick, the dough will be heavy, and the crust will form before the steam can puff up the bread.