Changing the margins in LaTeX

Don't do it. Learn some LaTeX, produce some documents, and then ask again.

You can never change the margins of a document by software, because they depend on the actual size of the paper. What you can change are the distances from the apparent top and left edges of the paper, and the width and height of the text. Changing the last two requires more skill than you might expect. The height should bear a certain relationship to \baselineskip. And the width should not be more than 75 characters. Lamport's warning in his section on `Customizing the Style' really must be taken seriously. One-inch margins on A4 paper are fine for 10- or 12-pitch typewriters, but not for 10pt type (or even 11pt or 12pt) because so many characters per line will irritate the reader. However...

Perhaps the easiest way to get more out of a page in LaTeX is to get macros/latex209/contrib/misc/fullpage.sty, which sets the margins of the page identical to those of plain TeX, i.e., 1-inch margins at all four sides of the paper. It also contains an adjustment for A4 paper.

Somewhat more flexible is macros/latex/contrib/other/misc/vmargin.sty, which has a canned set of paper sizes (a superset of that provided in LaTeX2e), provision for custom paper, margin adjustments and provision for two-sided printing.

For details of LaTeX's page parameters, see section C.5.3 of the LaTeX manual (pp. 181-182). The origin in DVI coordinates is one inch from the top of the paper and one inch from the left side; positive horizontal measurements extend right across the page, and positive vertical measurements extend down the page. Thus, for margins closer to the left and top edges of the page than 1 inch, the corresponding parameters, i.e., \evensidemargin, \oddsidemargin, \topmargin, can be set to negative values.

You cannot simply change the margins of part of a document within the document by modifying the parameters shown in Lamport's figure C.3. They should only be changed in the preamble of the document, i.e., before the \begin{document} statement. To adjust the margins within a document we define an environment:

\newenvironment{changemargin}[2]{%
 \begin{list}{}{%
  \setlength{\topsep}{0pt}%
  \setlength{\leftmargin}{#1}%
  \setlength{\rightmargin}{#2}%
  \setlength{\listparindent}{\parindent}%
  \setlength{\itemindent}{\parindent}%
  \setlength{\parsep}{\parskip}%
 }%
\item[]}{\end{list}}

This environment takes two arguments, and will indent the left and right margins by their values, respectively. Negative values will cause the margins to be narrowed, so \begin{changemargin}{-1cm}{-1cm} narrows the left and right margins by 1cm.