Siehe Option `delta` in der Anleitung [Anleitung von [Paket `pdfpages`](https://ctan.org/pkg/pdfpages):
Paket `pdfpages`](http://mirrors.ctan.org/macros/latex/contrib/pdfpages/pdfpages.pdf):
\documentclass{article}
\usepackage{pdfpages}
\begin{document}
\includepdfmerge[nup=2x3,delta=2mm 2mm]{
example-image-a.pdf, 1,
example-image-b.pdf, 1,
example-image-c.pdf, 1,
example-image-a.pdf, 1,
example-image-b.pdf, 1,
example-image-c.pdf, 1,
}
\end{document}
