Place cranberry juice, sugar and cinnamon stick into a large saucepan. Bring to a simmer over medium heat and simmer until the sugar dissolves.
Place the pears into the simmering juice and cover. Cook until the pears are tender, turning occasionally, 15 to 20 minutes. Once tender, remove the saucepan from the heat and set aside to cool to room temperature. Turn the pears a few times as they cool so the colour remains even.
If Bosc pears are unavailable, use conference pears instead.