A rudimentary approach to this would be to use fancyhdr
to set the page number of the left and right column using \lfoot
and \rfoot
respectively. The following MWE does exactly that:

\documentclass{article}
\usepackage[landscape,twocolumn]{geometry}% http://ctan.org/pkg/geometry
\usepackage{fancyhdr,lipsum}% http://ctan.org/pkg/{fancyhdr,lipsum}
\pagestyle{fancy}
\fancyhf{}% Clear header/footer
\lfoot{\makebox[\columnwidth]{\thepage}}
\rfoot{\makebox[\columnwidth]{\number\numexpr\value{page}+1}\stepcounter{page}}
\begin{document}
\lipsum[1-20]
\end{document}
The right-hand column "page number" is calculated, and also steps the page
counter to avoid duplication on subsequent pages. One problem might be that there will always be two "page numbers" on a page. Another issue inherent to this approach would be the use of page references, which will be incorrect.
The separation between columns is set by the length \columnsep
, which you can change using
\setlength{\columnsep}{<len>}
where you specify <len>
.
multicol
package does something like that, albeit I'm not sure how it works over multiple pages. – bodo Feb 9 '13 at 7:08