Place chopped pears into a large pot, and pour pineapple juice over them to prevent them from browning. Stir in sugar, and bring to a boil over medium-high heat. Stir frequently to prevent scorching. When the pears are at a full boil, reduce heat to medium, and cook until the mixture is the color and texture of honey. The longer you cook it, the thicker it gets. Cooking time is usually 2 to 3 hours.
Ladle into hot sterile jars, filling to within 1/4 inch of the top. Wipe rims with a clean damp cloth, and seal jars with lids and rings. Process in a boiling water canner for 10 minutes, or the amount of time recommended by your local extension for your area.