Asian pears are a low-acid fruit. Consequently, for safe canning, the USDA recommends some acidity be added to the jars. Here is a walk-through of their safety guidelines.
Wash and peel the pears. Slice the pears in half, and core them. Cut into slices if desired, or leave as halves. Put pieces into water with some lemon juice (or ascorbic acid) in it as you are working so they won't brown on you.
Drain pear pieces and discard soaking water, put in a large pot of boiling water, bring water back to the boil and boil for 5 minutes.
Pack fruit loosely into hot jars, leaving 3 cm (1 inch) headspace.
To each half-litre (US pint) jar, add 1 tablespoon lemon juice; OR To each litre (US quart) jar, add 2 tablespoons lemon juice.
Fill jars with the blanching water, leaving 2 cm (½ inch) headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process half-litre (US pint) jars for 20 minutes; litre (US quart) jars for 25 minutes.
Increase time as needed for your altitude.
Notes
Tip: if you're going to slice the pears, then it's faster to quarter the pears, which allows you to quickly slice the cores out, then slice up the quarters.