documentclass[whitelogo]{tudelft-report}
usepackage{pdfpages}

begin{document}
begin{minipage}{textwidth}
includepdf[fitpaper= true, pages=-]{paper.pdf}
end{minipage}
end{document

documentclass{report}
usepackage{pdfpages}

begin{document}
pagecolor{white}
%nopagecolor % without it the picture is lost:
includepdf[fitpaper= true, pages=-]{example-image.pdf}

end{document}

documentclass{report}
usepackage{xcolor}
pagecolor{white}
usepackage{pdfpages}

begin{document}
pagecolor{white}
includepdf[fitpaper= true, pages=-]{example-image.pdf}

end{document}