\documentclass{article}
\usepackage{graphicx}
\begin{document}
\begin{center}
\includegraphics[width=4in]{safe/1pd.pdf}

\includegraphics[width=4in]{safe/1pf.pdf}

\includegraphics[width=4in]{safe/2pd.pdf}

\includegraphics[width=4in]{safe/2pf.pdf}

\includegraphics[width=4in]{safe/3pd.pdf}

\includegraphics[width=4in]{safe/3pf.pdf}
\end{center}
\end{document}