This is a simple jam that's easy to make and easier to eat.
In a suitable pot, combine pears and plums. Stir in pectin. Bring to a full rolling boil over high heat, stirring constantly.
Stir in sugar; return to a full rolling boil. Boil for 1-minute, stirring constantly.
Remove from the heat; skim off foam. Pour into jars or freezer containers and cool to room temperature (about an hour). Cover and let stand overnight or until set, but not longer than 24 hours.
Refrigerate or freeze.