LaTeX assumes that the origin is 1in down from the top of the paper and 1in in from the lefthand side of the paper. \hoffset and \voffset, which should be used for resetting the origin, will be ignored in the following.
\textheight is given in the standard documentstyle in terms of the number of lines of text. So in 10pt article
\textheight = 43\baselineskipi.e., a page of solid text with no sections, figures, ... should be 43 lines. This method lowers the number of underfull vbox error that will appear. To calculate the actual values you need to know the baselineskip (12pt for 10pt styles) and topskip (also 12pt) so the actual \textheight is 528pt (~7.3in). That means the bottom margin (including foot) is 2.3in.
\advance\textheight by \topskip
Printers sometimes don't place the origin correctly and sometimes what the printer thinks is 1in isn't. You can use the \advance commands to do some minor fixing.
\advance\oddsidemargin by -.1indecreases the leftmargin .1in (i.e., moves the text .1in to the left on the page, no change in textwidth). Actually one should use \hoffset and \voffset to do this to ensure that (0,0) is 1 inch from the leftside and top of the paper. If one was intent upon using proper LaTeX, the command should be
\addtolength{\oddsidemargin}{-.1in}instead of
\advance\oddsidemargin by -.1inThe two forms are equivalent.
For a visual demonstration of the margin parameters,
latex latex-margins.texand print the output.
\advance\textwidth by X
\advance\oddsidemargin by -X/2
\advance\evensidemargin by -X/2
\advance\textwidth by 2X
\advance\oddsidemargin by -X
\advance\evensidemargin by -X
\def\quote{\list{}{\rightmargin\leftmargin}\item[]}My first pass is the definition
\let\endquote=\endlist
\def\changemargin#1#2{\list{}{\rightmargin#2\leftmargin#1}\item[]}Where
\let\endchangemargin=\endlist
\begin{changemargin}{1in}{.5in}Changes the left and right margins to 1in and .5in. Reading report.doc code for quotation and quote environments and the description of the list parameters in the manual will allow you to fine tune (for instance the above does not have paragraph indentation but does have space between paragraphs).
\end{changemargin}ends the changed margin area.