Boil jars on rack in large pot with water 10 minutes. Place flat lids in saucepan with water. Bring to boil; remove from heat. Let stand in hot water until ready to fill. Drain well.
Prepare fruit and measure fruit (or juice for jelly) into 6 to 8 quart pot along with lemon juice (if called for in recipe). Measure sugar into separate bowl. (Scrape extra sugar from cup with spatula to level for exact measure.)
Stir sugar into fruit or juice. Mix well. Add 1/2 teaspoon butter. Bring mixture to full rolling boil over high heat, stirring constantly. Open Certo fruit pectin pouch(es) and quickly stir contents into fruit mixture. Bring to full rolling boil and boil 1 minutes, stirring constantly. Remove from heat. Skim off any foam.
Fill all jars immediately to 1/8 inch of tops. Wipe jar rims and threads. Cover quickly with flat lids. Screw threaded bands tightly. Invert jars for 5 minutes, then turn upright. After 1 hour check seals, or use USDA water method.