  We provide a unified treatment of electric-magnetic duality, at the action
level and with manifest Lorentz invariance, for massive, massless as well as
partially-massless gravitons propagating in maximally symmetric spacetimes of
any dimension n>3. For massive and massless fields, we complete previous
analyses that use parent-action techniques by giving dual descriptions that
enable direct counting of physical degrees of freedom in the flat and massless
limit. The same treatment is extended to the partially-massless case, where the
duality has been previously discussed in covariant form only at the level of
the equations of motion. The nature of the dual graviton is therefore clarified
for all values of the mass and of the cosmological constant.
