Slice the rhubarb into 1/2 inch slices. Add 2 cups of sugar, orange juice, and vanilla to the rhubarb in a heavy saucepan. Mix well and set aside.
Peel, core, and dice the pears. Place cut pears in water containing ascorbic acid until all the pears are diced. Add the rest of the sugar, orange peel, mace, and cinnamon to the rhubarb mixture. Stir well and bring to a boil.
Drain the pears, add to the mixture and cook for 3 minutes longer.
Ladle into hot jars. Release the air bubbles, clean the rims, seal, and process in a water bath or 25 minutes.