Can you evolve benched Pokemon

Yes, you can evolve any Pokémon that are within your Pokémon party but provided they are in your PC or in the Daycare then you cannot evolve your Pokémon. Additionally for games like Pokémon Black, Pokémon White, Pokémon Black 2 and Pokémon White, Pokémon cannot evolve while they're in the Dream World on the Global Link feature.