Heat oven to 350° F. On a lightly floured surface, place one piecrust on top of the other and roll out the stack to form one 16-inch circle. Transfer to a parchment-lined baking sheet. Spread 1/4 cup of the preserves on the crust, leaving a 2-inch border.
In a large bowl, toss the apples, pears, flour, lemon juice, ginger, cinnamon, and 3 tablespoons of the sugar. Transfer to the crust, leaving the border clear. Fold the edges of the crust over the fruit mixture.
Brush the egg on the crust and sprinkle with the remaining teaspoon of sugar. Bake until the crust is golden brown and the fruit is tender, 50 to 60 minutes.
In a small saucepan, heat the remaining 2 tablespoons of preserves and 1 tablespoon water over medium heat until liquid, 2 to 3 minutes. Brush on the fruit. Serve warm or at room temperature.