Cut off the skins and the ends off the pineapples.
Cut in half lengthways and then each half in half again lengthways. You should have 4 pieces of pineapple now.
Slice the cores off the 4 pineapple pieces.
Cut the pineapple into diced-sized pieces.
Add the pineapple to a big pot and cover with water. Add in the sugar now if you are using it.
Bring the water, sugar, and pineapple to a boil and then turn the heat off.
Get the pressure canner ready by adding 3L (quarts) of water to the canner. Place the spring form ring in the bottom of the PC and then the canner rack.
Ladle the pineapple into hot clean jars and wipe the rims clean and use new seals. place the rings on the jar and screw them down until they are fingertip tight.
Place your jars into the canner and steam can for 10 minutes.
Remove jars from canner and cool on the bench. Once cooled store in a cool dark cupboard.