Merging PDF with latex

Use pdfpages package in the packet manager, if necessary. Specially in windows 7 I had to install the pdfpackage.sty using packet manager as an admin.

\documentclass{article}

\usepackage{pdfpages}

\begin{document}

\includepdfmerge{One.pdf,-}

\includepdfmerge{Two,-}

\includepdfmerge{Three_part.pdf, 3-14} % mention range

\end{document}