\documentclass[12pt,a4paper,english]{article}
\usepackage{fixltx2e}%% the official fixes for LaTeX2e
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{url}
\usepackage{lineno}
\usepackage{babel}
\makeatother
\begin{document}

\title{Numbered or marked lines}
\author{Herbert Voß}
\date{\today}
\maketitle
\begin{abstract}
The package is availabe at \TeX{} Archive Network (CTAN) or by the
author \url{http://www.desy.de/~stephan/tex/lineno/}. Take care that
you always use the latest version. Just as all other packages declare
it in the \LaTeX{} preamble with \texttt{\textbackslash{}usepackage\{lineno\}.}
\end{abstract}

\section{Numbered lines}
\begin{linenumbers}

Without any options the lines are numbered by default with the following
values:

\begin{verbatim}
\linenumberwidth=10pt
\linenumbersep=10pt
\modulolinenumbers[1]
\quotelinenumbersep=\linenumbersep
\def\linenumberfont{\normalfont\tiny\sffamily}
\end{verbatim}
You can change these values in the usual way.

\end{linenumbers}

The next paragraph has the values
\begin{verbatim}
\linenumberwidth=30pt
\linenumbersep=5pt
\modulolinenumbers[2]
\quotelinenumbersep=\linenumbersep
\def\linenumberfont{\normalfont\small\sffamily}
\end{verbatim}

\linenumberwidth=30pt
\linenumbersep=5pt
\modulolinenumbers[2]
\quotelinenumbersep=\linenumbersep
\def\linenumberfont{\normalfont\small\sffamily}

\begin{linenumbers}

it follows a nonsense text for demonstration that the counter continues:

\begin{verse}
As the name says this are always math expressions which are in a standard
textline, like this one:.. There are no limitations for the height
of the math expressions, so that the layout may be very lousy if you
insert a big matrix in an inlinemode like this: this case it's better
to use the displaymathmode (Chapter page ).~
\end{verse}
If you like the numbers on the right side of the page, change the
option with \textbackslash{}rightlinenumbers. The resetting of the
counter can be done with (for example): \texttt{\textbackslash{}resetlinenumber{[}5{]}}.
Pay attention for the square brackets!

\resetlinenumber[5]
\rightlinenumbers
\linenumberwidth=10pt
\modulolinenumbers[1]
\quotelinenumbersep=\linenumbersep
\def\linenumberfont{\normalfont\tiny\sffamily}

it follows a nonsense text for demonstration that the counter continues:

As the name says this are always math expressions which are in a standard
textline, like this one:.. There are no limitations for the height
of the math expressions, so that the layout may be very lousy if you
insert a big matrix in an inlinemode like this: this case it's better
to use the displaymathmode (Chapter page ).~

\leftlinenumbers


\section{Marked lines}

If you like to mark some lines with any character, you can redefine
the commands \textbackslash{}thelinenumber with 

\begin{verbatim}
\renewcommand\thelinenumber{>}
\end{verbatim}
\def\linenumberfont{\normalfont\normalsize\sffamily}

\renewcommand\thelinenumber{>} and you'll get quoted lines just in
an email reply.

it follows a nonsense text for demonstration that the counter continues:

\begin{verse}
As the name says this are always math expressions which are in a standard
textline, like this one:.. There are no limitations for the height
of the math expressions, so that the layout may be very lousy if you
insert a big matrix in an inlinemode like this: this case it's better
to use the displaymathmode (Chapter page ).
\end{verse}
On the other hand you can redefine the command \textbackslash{}makelinenumber
with

\begin{verbatim}
\renewcommand\makeLineNumber{\hss !\ \rlap{\hskip\textwidth\ !}}
\end{verbatim}
\renewcommand\makeLineNumber{\hss !\ \rlap{\hskip\textwidth\ !}} to
get bothsided marked text. it follows a nonsense text for demonstration
that the counter continues:

As the name says this are always math expressions which are in a standard
textline, like this one:.. There are no limitations for the height
of the math expressions, so that the layout may be very lousy if you
insert a big matrix in an inlinemode like this: this case it's better
to use the displaymathmode (Chapter page ).

\end{linenumbers}
\end{document}