Preheat oven to 375 degrees F and line a large baking sheet with parchment paper (you may have to do this in 2 batches, depending on the size of your baking sheet). Lightly flour a flat surface and roll out the puff pastry sheet to 1/8-inch thickness (into approximately a 12×18-in. rectangle). Using a sharp knife, cut dough into four equal squares.
Place the dough squares onto the prepared baking sheet and top with equal amounts of the cheese, peaches and raspberries, leaving a 1-inch border around each side. Fold over the edges and pinch together at corners.
Sprinkle the sugar over the fruit and brush the exposed dough with the melted butter. Bake in the preheated oven for 20 minutes, or until edges are golden brown. Serve warm!