Candi Pawon is small enough to miss if you rush straight to Borobudur, but it belongs to the same ritual and geographic landscape. The temple sits between Mendut and Borobudur, and its proportions, reliefs, and position make it a useful stop for understanding the wider Buddhist complex rather than just the great monument.
Visit it on the way to or from Borobudur, ideally with Mendut as well. The scale is intimate, so the reward is in slowing down: looking at the carved stone, noticing the alignment, and seeing how the famous temple sits within a chain of older sacred places.