Pastry flour is of course for making pastry.
Pastry flour is ideal for making pastry that is flaky and tender.
Sometimes using regular bleached all purpose flour can result in a tough crust that is not very flaky or not flaky at all.
Cake flour will make pastry too tender and it will probably fall apart.
You can buy your own pastry flour.
Or you can make your own.
I make my own since where I live pastry flour can be hard to find.
To make your own you will need:
4 cups bleached all purpose flour
2-1/4 cups cake flour
Mix them well to blend.
It makes 6-1/4 cups pastry flour.
If you have the space, I suggest storing it in the freezer. Pastry is best made with really cold ingredients.