  We study a class of models in which the Standard Model (SM) and dark matter
(DM) belong to a conformal/scale-invariant theory at high energies. Scale
invariance is spontaneously broken at scale $f$, giving rise to a dilaton as
the corresponding Goldstone boson. In the low energy theory, we assume that DM
interacts with the SM solely through the dilaton portal, which is suppressed by
the conformal breaking scale $f$. For $f\gg{\rm TeV}$, the portal interactions
are extremely weak, resulting in DM not being in thermal equilibrium with the
SM. Thus, ultraviolet freeze-in production of DM occurs through the dilaton
portal, being most effective at the maximum temperature of the SM bath. The
temperature evolution is greatly impacted by the reheating dynamics, which we
parametrize using a general equation of state $w$ and temperature at the end of
reheating $T_{\rm rh}$. We analyze the implications of the reheating dynamics
for DM production in this framework and identify regions of parameter space
that result in the observed DM relic abundance for a wide range of DM masses
and reheating temperatures for scalar, vector, or fermion DM.
