Hi, Fred,
Depends on what you mean by "one page".
If you format a letter-size (8.5x11-inch) document in landscape orientation
and set the left/right margins to 0.5 inch, you can fit 132 columns of
9-point Courier New.
If you have to squeeze the same text onto a portrait page with the same
margins, you'll have to reduce the point size to 6.5 point. You can do that
by selecting the text, typing 6.5 into the size box on the toolbar, and
pressing Enter.
For other pages sizes or margin widths, you need to know that for Courier
New the point size and the pitch (characters per inch) are related: their
product is always 120. By doing some reasonably simple algebra, you can find
that the point size needed to fit 132 characters into a given column width
is 0.91 times the width in inches, rounded down to the nearest 0.5 point.