have you tried one of the larger operators of the An-12 like Volga Dnepr or even some of the Bulgarian operators? (look up contact info in JP Fleets or similar).I'm sure that being more 'westernised' airlines,they might well have documentation in English.Alternatively,this is just a flyer,try Antonov itself,or ADB?i'm sure they have translated literature.
Good luck.Cb