I'm parsing PDFs generated by ArcGIS Pro 2.4-2.7. I'm having difficulties predicting the order in which label classes are drawn to the PDF. This is important because in some cases the label class optional content groups written to the PDF have duplicate names, so I cannot rely on identifying them by name alone.
Initially, it seemed that the rules for an entire map were driven by map layer order and label class priority like this:
1. Draw all unprioritized label classes first, in layer draw order.
2. Draw all prioritized label classes, in priority order.
But since I've found maps where it seems label classes within a layer are drawn as a group, in the order I initially thought applied to the map as a whole, and the groups are drawn in layer draw order.
But I have a map where one layer's labels seem inexplicably to be drawn out of layer draw order.
I haven't managed to resolve logic than successfully predicts label class order for all of my test maps. Is there a published rule set? Is there some other property besides layer draw order and label class priority that determines label class draw order?
TIA for any knowledge.