Thank you for your question, Colleen.  I wonder if you might provide a bit more information about your pear tree.  First, are you able to take a photo of the underside of an affected leaf?  Second, do you have juniper plants anywhere in the area?  I'm trying to determine if your plant has a rust disease (fungus), and it would help to narrow down the possibilities.  Thanks!

Another expert has suggested the cause of this is a mite, causing blisters on the leaf. Here is an article on the pest:  https://pnwhandbooks.org/insect/tree-fruit/pear/pear-eriophyid-mite

Applying a lime-sulfur spray in the spring and fall, or a superior oil as buds begin to swell, are the only chemical solutions available to homeowners.  Hope this helps.  Good luck!