\documentclass{book}

% This packages does all the magic
\usepackage{pdfpages}

% Drop pagenumbers
\pagenumbering{gobble}

% Let's merge a bunch of documents
\begin{document}

% Masterarbeit
\includepdf[pages=-]{build/MA-Master.pdf}

% Clientdokumentation
\cleardoublepage % Make sure we clear to an odd page
\includepdf[pages=-]{build/CLNT-DOC-Master.pdf}

% CA-Dokumentation
\cleardoublepage
\includepdf[pages=-]{build/CA-DOC-Master.pdf}

% Serverdokumentation
\cleardoublepage
\includepdf[pages=-]{build/SRV-DOC-Master.pdf}

\end{document}