Crop a PDF with Latex

\documentclass{article}
\usepackage{graphicx}
\usepackage[active,tightpage]{preview}
\PreviewMacro[{*[][]{}}]{\includegraphics}
\begin{document}
\pagestyle {empty}

\includegraphics[viewport=0 270 420 570]{NawrockiFig-crop.pdf}

\end{document}