\documentclass{article}

\usepackage[cmyk]{xcolor}%
\usepackage{tikz}%
\usepackage{pgf}%
\usetikzlibrary{fadings}%

\usepackage{pgfpages}%
\pgfpagesuselayout{resize to}[a4paper]

\begin{document}

\begin{tikzpicture}[remember picture,overlay]
    \shade [top color=yellow,bottom color=red!50] (current page.north west) rectangle (current page.south east);%
\end{tikzpicture}

\centerline{\Huge Hi Parsi\LaTeX{}}
\end{document}