Starting with an additive process (Y t ) t≥0 , it is in certain cases possible to construct an adjoint process (X t ) t≥0 which is itself additive. Moreover, assuming that the transition densities of (Y t ) t≥0 are controlled by a natural pair of metrics d ψ,t and δ ψ,t , we can prove that the transition densities of (X t ) t≥0 are controlled by the metrics δ ψ,1/t replacing d ψ,t and d ψ,1/t replacing δ ψ,t .