  We show Poincar\'e Duality for $\mathbf{F}_p$-\'etale cohomology of a smooth
proper rigid-analytic space over a non-archimedean field $K$ of mixed
characteristic $(0, p)$. It positively answers the question raised by P.
Scholze in [Sch13a]. We prove duality via constructing Faltings' trace map
relating Poincar\'e Duality on the generic fiber to (almost) Grothendieck
Duality on the mod-$p$ fiber of a formal model. We also formally deduce
Poincar\'e Duality for $\mathbf{Z}/p^n\mathbf{Z}$, $\mathbf{Z}_p$, and
$\mathbf{Q}_p$-coefficients.
