Mixing KOMAscript and geometry

The geometry package has a very useful option, namely pass.

If you call

\usepackage[pass]{geometry}

the package will not set any pagination parameter, but just load itself and make the \newgeometry command available.

An example of usage is in the package documentation:

\documentclass{book}
\usepackage[pass]{geometry}
   % ’pass’ disregards the package layout,
   %  so the original ’book’ layout is memorized here.
\begin{document}
\newgeometry{margin=1cm}% changes the first page dimensions.
   Page 1
\restoregeometry % restores the original ’book’ layout.
   Page 2 and more
\end{document}

For several release KOMA-Script provides an undocumented option usegeometry to interact with package geometry. Since KOMA-Script 3.22 this is an documented option (of package typearea). It translates the page settings of package typearea into page settings of package geometry and passes them, e.g., as options to geometry.

\documentclass[usegeometry]{scrreprt}
\usepackage{geometry}
\usepackage{showframe}
\begin{document}
\newgeometry{margin=1cm}% changes the first page dimensions.
   Page 1
\restoregeometry % restores the original typearea layout.
   Page 2 and more
\end{document}

The cooperation makes it even possible to change page size or page orientation using typearea and then change the margins using geometry, something current geometry does not provide using \newgeometry. But in this case you should use typearea's commands to store and restore the geometries.