Grind strawberries and cranberries in a food processor or grinder; place in a Dutch oven. Add sugar. Bring to a full rolling boil; boil for 1 minute. Remove from the heat; stir in pectin and return to a full rolling boil. Boil for 1 minute, stirring constantly. Remove from the heat.
Cool for 5 minutes; skim off foam. Carefully ladle hot mixture into hot half-pint jars, leaving 1/4-in. headspace. Remove air bubbles; wipe rims and adjust lids. Process for 10 minutes in a boiling-water canner.
Canning Altitude Jam-Jelly
The processing time listed is for altitudes of 1,000 feet or less. Add 1 minute to the processing time for each 1,000 feet of additional altitude.
Heat 3 tablespoons light corn syrup in microwave until warm; gently toss with 1 cup fresh or frozen cranberries, allowing excess syrup to drip off. Toss in 1/3 cup sugar to coat. Place on waxed paper; let stand until set, about 1 hour.