  We investigate the consequences of heavy quark spin symmetry (HQSS) on
hidden-charm pentaquark $P_c$ states. As has been proposed before, assuming the
$P_c(4440)$ and the $P_c(4457)$ as $S$-wave $\bar{D}^*\Sigma_c$ molecules,
seven hadronic molecular states composed of $\bar{D}\Sigma_c$,
$\bar{D}\Sigma_c^*$, $\bar{D}^*\Sigma_c$, and $\bar{D}^*\Sigma_c^*$ can be
obtained, with the $\bar{D}\Sigma_c$ molecule corresponding to the $P_c(4312)$.
These seven states can decay into $J/\psi N$ and $\eta_c N$, and we use HQSS to
predict ratios of partial widths of the $S$-wave decays. For the decays into
$J/\psi N$, it is found that among all six $P_c$ molecules with spin $1/2$ or
$3/2$, at least four states decay much more easily into the $J/\psi N$ than the
$P_c(4312)$, and two of them couple dominantly to the $\bar D^*\Sigma_c^*$.
While no significant peak around the $\bar{D}^*\Sigma_c^*$ threshold is found
in the $J/\psi p$ distribution, these higher $P_c$ states either are produced
with lower rates or some special production mechanism for the observed $P_c$
states might play an important role, such as an intricate interplay between the
production of pentaquarks and triangle singularities.
