Optimally you would juice them and add the juice to a secondary fermenter. Alternatively you can just peel and chop, or peel and puree them. I have peeled and chopped apples before and froze them, then added them right to primary at yeast pitching time. It worked great. The yeast will find the sugars, they sucked the sugars right out of the apples...that is for sure.
You know, a nice fall style pear ale sounds AWESOME. Try this maybe.
5 gallon batch
9 pounds two row
8 oz special B
8 oz caramunich
4 oz aromatic
4 oz biscuit
2 oz chocolate malt
add 5 # chopped and peeled pears to primary and let the yeast work their magic.
I wouldn't be against adding a cinnamon stick and a nutmeg at the end of the boil too....
30 IBU magnum or whatever you got at 60 and call it good.