We need to cut the pumpkins into cubes. First, cut the stem out like you are getting ready to carve a jack-o-lantern. Then cut the pumpkin into four or five wedges. Use a spoon to scrape out the pumpkin guts.Peel the pumpkin. I was very thankful my vegetable peeler worked for this. However, if you are dealing with pumpkins with a super-hard rind, you might need a sharp knife to remove the peel instead. Watch those fingers! Cut the peeled pumpkin into (roughly) 1-inch cubes.
Place the cubes in a large pot and cover with water.
Boil for 2 minutes, then place the pumpkin cubes into hot jars. (Avoid smashing down the cubes as much as possible!)
Cover the pumpkin cubes with the leftover hot cooking liquid, leaving 1-inch of headspace.
Add lids and rings and place into your pressure canner. Process quart jars for 90 minutes at 15 pounds pressure. Process pint jars for 55 minutes at 15 pounds pressure.
When you are ready to make pumpkin puree, simply open a jar, strain out the liquid, and mash! I found one jar of drained, mashed pumpkin gave me around 2-3 cups of puree.