Prepare boiling water canner. Heat jars and lids in simmering water until ready for use. Do not boil. Set bands aside.
Combine prepared apricots with lemon juice and sugar in a 6 or 8-quart saucepan. Add up to 1/2 teaspoon butter or margarine to reduce foaming, if desired. Bring mixture to a full rolling boil that cannot be stirred down, over high heat, stirring frequently.
Add pectin, immediately squeezing entire contents from pouch. Continue hard boil for 1 minute, stirring constantly. Remove from heat. Skim foam if necessary
Ladle hot jam into hot jars leaving 1/4 inch headspace. Wipe rim. Center lid on jar. Apply band until fit is fingertip tight.
Process jars in a boiling water canner for 10 minutes, adjusting for altitude. Remove jars and cool. Check lids for seal after 24 hours. Lid should not flex up and down when center is pressed.