  We determine conformal symmetry classes for the pp-wave spacetimes. This
refines the isometry classification scheme given by Sippel and Goenner (1986
{\it Gen. Rel. Grav.} {\bf 18} 1229). It is shown that every conformal Killing
vector for the null fluid type $N$ pp-wave spacetimes is a conformal Ricci
collineation. The maximum number of proper non-special conformal Killing
vectors in a type $N$ pp-wave spacetime is shown to be three, and we determine
the form of a particular set of type $N$ pp-wave spacetimes admitting such
conformal Killing vectors. We determine the conformal symmetries of each type
$N$ isometry class of Sippel and Goenner and present new isometry classes.
