\documentclass[a4paper]{article}
%\VignetteIndexEntry{Manual of lasso2 package}
%\VignettePackage{lasso2}

\usepackage{pdfpages}

\begin{document}

\newread\PDFtoInclude
\openin\PDFtoInclude=Manual-wo-help.pdf
\ifeof\PDFtoInclude
\typeout{No file Manual-wo-help.pdf}
\else
\includepdf[fitpaper=true,pages=-]{Manual-wo-help.pdf}
\fi

\end{document}
