That looks like mite damage from the pearleaf blister mite (Eriophyes pyri), a very small microscopic Eriophyid mite. Pearleaf blister mite feeding on leaves causes reddish to yellowish green blisters; blisters turn brown or black as the tissue dies later in the season. They also feed on the fruit which can cause russetting. The damage to the leaves is cosmetic, but if severe enough can cause leaves to distort and fall off prematurely. A spray with lime sulfur in the fall after harvest and a dormant oil in late winter or early spring, before the buds swell, is the best treatment. For more information, refer to the PNW Pest Management Handbook: https://pnwhandbooks.org/insect/tree-fruit/pear/pear-eriophyid-mite
and WSU Hortsense: https://hortsense.cahnrs.wsu.edu/fact-sheet/ornamental-pear-pearleaf-blister-mite/.