This looks like a fungal disease, such as pear scab or Fabraea leaf spot. Fungal diseases can be controlled prophylactically with a preventative fungicide, but infected leaves and fruit cannot be cured. More information is available below. There is also leaf scorch evident in the photo, which could be caused by a disease or environmental conditions, such as the heat and drought we have been experiencing. It is important to determine how the trees have been cared for, whether they have been irrigated, etc. The tree in the photo is likely to recover, but I would recommend a preventative fungicide program next spring if it is a wet spring. 

https://www.canr.msu.edu/ipm/diseases/pear_scab

https://www.canr.msu.edu/ipm/diseases/fabraea_leaf_spot#gallery

https://netreefruit.org/pears/diseases/fabraea-leaf-spot

https://netreefruit.org/pears/diseases/pear-scab