Preheat oven to 425 F. Line a baking sheet with parchment paper; set aside.
In a large bowl, combine fruit. In another bowl, whisk together sugar, flour, cornstarch & cinnamon. Gently toss into fruit mixture along with lemon juice.
Cut thawed, cold puff pastry sheets into circles or squares (your choice). Put a spoonful of filling in the center of each & bring the corners together enclosing the filling. Place pastries on baking sheet & sprinkle with coarse sugar.
Bake for about 12-15 minutes or until golden. Remove from oven & allow to cool for 5 minutes on baking sheet then transfer to a wire cooling rack.
This amount of filling is enough for a large deep dish 9-inch pie. It can be easily halved for a small amount of pastries if you wish.