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.
To each half-litre (US pint) jar, add 1 tablespoon lemon juice; OR To each litre (US quart) jar, add 2 tablespoons lemon juice.
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.