Talking of high altitude AD, the Cub had a pressurised crew compartment and an pressurised freight bay. I don't know if the freight bay could be separately pressurised.
I'm sure that was a typo PN, as the standard Transport Cub "A" (An 12 BP) of course had an unpressurised freight bay and was (IIRC)) limited to around 5000m with troops.
The ELINT Cubs were a different matter , B to D etc. and some at least had pressurisation in the main cabin , operating quite a bit higher - as you will probably recall.