To begin prepare your canning supplies. The jars should be inspected, clean, and hot.
Combine the crushed pears, chopped cranberries, apple juice, lemon juice, sugar, and cinnamon in a large, non-reactive pot.
Bring the mixture to a rolling boil over medium high heat. Boil for 1 minute, stirring continually.
Add the butter and liquid pectin.
Bring the mixture to a rolling boil and boil hard for 1 full minute. Stir continually.
Remove it from the heat. If you do not add the butter, skim the foam from the top.
Ladle the jelly into the prepared hot jars, leaving 1/4 inch of headspace.
Remove any air bubbles with a bubble wand.
Wipe the rim of the jar with a damp cloth dipped in white vinegar to remove any residue.
Place a lid and ring on the jar, finger tight.
Process the jars for 10 minutes. (Adjust for Elevation)
Carefully transfer the jars to an out of the way place away from drafts. I generally line the counter with a folded dish towel or use my canning mat that a subscriber made for me.
Allow the jars to cool undisturbed for 24 hours, or at least overnight.
The next day remove the rings, test the seals, label the jars, and store in your pantry.
If a jar didn't seal, place it in your refrigerator to use.
Enjoy!
Notes
To Prevent the Pears from Discoloring: As you dice your pears, place them in a large bowl filled with cold water, with lemon juice, citric acid or ascorbic acid in it. I find the acids work best. Use the amount suggested on the container instructions. Rinse and drain will before crushing them to make the jam.