Peel and core pears; cut into chunks. To a large pot on top of the stove, add pears, lemon juice, sugar and ginger. (Use less sugar if the pears are ripe and sweet.) Bring to a boil; reduce heat and simmer for 45 minutes, or until the pears are soft.
Using an immersion blender, purée the mixture until it is smooth. (You may need to transfer the pear mixture to a large mixing bowl to avoid damaging a non-stick pot.) A food processor can be used if an immersion blender is not available; cool mixture slightly before processing.
Add cinnamon to puréed mixture; mix well.
Fill sterilized jars with pear sauce to the top of the jar. Wipe rims clean, seal with lids and rings. Store jars in refrigerator for up to 1 week.
Fill sterilized jars with pear sauce, leaving a 1/4-inch space at the top. Wipe rims clean, seal with lids and rings. Using tongs, place the jars into a hot water bath; be sure that the jars do not touch one another, and are fully submerged. Cover the pot with the lid, heat water to a slow boil for about 10-15 minutes. Remove jars from pot. Store for up to 1 year in a cool, dry storage place.