Why doesn't this psframe include the right border of the poster? It colours just a square (see the output pdf picture). I'm compilating it with XeLaTeX.
\documentclass[landscape,a0paper,final]{a0poster}
\usepackage{fontspec}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{pstricks,pst-grad}
\usepackage{amsthm}
\begin{document}
\psframe[fillstyle=gradient,framearc=0,linewidth=1mm,gradmidpoint=
0,gradbegin=green,gradend=yellow](0,0)(1.\textwidth,-1.\textheight)
\end{document}

And its doing the same thing when I use psshadowbox around a minipage. But if it suppose to be out of that functional square, than it moves into new line.

\textwidthto\textheight, and there's an equal margin around the page border that will remain white. You can use something similar to Shading over a single page to shade withtikzusing page nodes. – Werner Apr 30 '14 at 23:16xelatex. Perhaps you have outdated packages. See Which package version am I using? and report back to us... – Werner Apr 30 '14 at 23:56