Wash, pare, core, and chop enough pears to make 3 cups of chopped fruit. Peel the orange, remove seeds, and chop the pulp. Place chopped pears in a large saucepan. Add orange pulp, pineapple, cherries, and lemon juice. Stir in pectin. Place on high heat and bring to a full rolling boil, stirring constantly. Add sugar, continue stirring, and heat again to a full rolling boil. Boil hard for one minute. Remove from heat and skim. Spoon into hot sterilized jars and seal.