Add some vertical text on the margin of document?

One way would be to use the background package:

Code:

\documentclass[10pt,a4paper]{article}
\usepackage[all]{background}
\usepackage{url}
\usepackage{lipsum}

\SetBgContents{\url{http://tex.stackexchange.com/}}% Set contents
\SetBgPosition{current page.west}% Select location
\SetBgVshift{-1.0cm}% Add vertical shift (results in a shift in x direction due to rotation)
\SetBgOpacity{1.0}% Select opacity
\SetBgAngle{90.0}% Select rotation of logo
\SetBgScale{2.0}% Select scale factor of logo

\begin{document}

\lipsum[1-7]

\end{document}

I usually use a combination of eso-pic, graphicx and rotating as it is easy to adjust in terms of location, angle and size.

\documentclass[12pt]{scrartcl}
\usepackage{blindtext}
\usepackage{eso-pic, rotating, graphicx}

\AddToShipoutPicture{\put(30,200){\rotatebox{90}{\scalebox{3}{Examiners copy}}}}

\begin{document}
\blindtext[4]

\end{document}