How can I prevent pear juice from soaking into pastry dough?
Whenever you're worried about something crisp being made soggy by something moist, the answer is usually fat. Brush the crust with butter or oil before you add the pears, and the oil will slow the absorption of water.

Alternately, dry out your pears. Cook them a bit. Roll them in sugar to dry them out some.

I'm surprised the pear juice is making it through the cheesecake batter. Usually that stuff keeps the liquids locked up tight. Maybe try a drier cheesecake, or one with a bit more egg?