Preheat the oven to 400°F and line a baking sheet with parchment paper.
Place the puff pastry sheet on the prepared baking sheet and gently roll out any creases.
In a bowl, toss peach slices with granulated sugar, brown sugar, cinnamon, and salt.
Arrange the peaches in the center of the pastry, leaving a 2-inch border.
Fold the edges of the pastry over the peaches, pleating as needed.
Brush the crust with beaten egg and sprinkle with coarse sugar.
Bake for 30–35 minutes or until golden and bubbly.
Allow to cool slightly before serving.