How to include (a) multipage pdf in the background

Question

I want to include one/several multipage PDFs as a background to print additional information on it (header, page number, ...)

Save the mwe Package documentation in the directory in order to work

\documentclass[oneside]{book}
\usepackage{mwe}
\usepackage{pdfpages}
\newcommand\invisiblesection[1]{%
  \refstepcounter{section}%
  \addcontentsline{toc}{section}{\protect\numberline{\thesection}#1}%
  \sectionmark{#1}}
\begin{document}
\pagestyle{headings}
\part{First}
\invisiblesection{My section}
% Only single pages
\AddToShipoutPictureBG*{\includegraphics[page=1]{mwe}}
.\pagebreak
\AddToShipoutPictureBG*{\includegraphics[page=2]{mwe}}
.\pagebreak
\AddToShipoutPictureBG*{\includegraphics[page=3]{mwe}}
.\pagebreak
% ...
\part{Second}
\invisiblesection{My section 2}
% No headers, ...
\includepdf[pages=1-]{mwe}
\end{document}