In a skillet, cook bacon over medium-high heat until crisp. Transfer bacon to paper towels, and discard all but 1 tablespoon bacon fat. Return the skillet to heat, and cook onion in reserved fat, 5 minutes, stirring frequently. Stir in celery and sage; cook until celery is soft, about 4 minutes. Stir in pears; cook 4 minutes more. Place stuffing cubes and bacon in a large bowl; toss with vegetable-and-pear mixture. Pour broth over mixture, stirring to mix well.
Coat a 9 x 13-inch baking dish with cooking spray. Fill with stuffing mixture. Dot with butter. Cover and refrigerate up to 3 days. On Thanksgiving Day, remove stuffing from refrigerator and bring to room temperature. Cover with foil, place in oven with turkey after turkey has cooked 2-1/2 hours, and bake 45 minutes. Uncover and bake 30 minutes more.