Two things may affect the number of lines per page.
One is the interaction of the margins, the line spacing (including space
before/after paragraphs), and the font size. With margins set to 1" and with
space before and after set to 0, you can get 25 lines per page in either of
these ways -- preferably by modifying the text's style rather than by direct
formatting:
- Set the line spacing to Exactly 25.9 pt. This will work with font sizes
from about 9 pt to 12 pt; outside those sizes, things start to look odd.
- Set the line spacing to Double and set the font size (for Times New Roman)
to 11.5 pt. (You can type this number into the font size box in the Format >
Font dialog even though you can't select half-point sizes from the
dropdown.)
The other factor is the group of settings on the Line and Page Breaks tab of
the Format > Paragraph dialog. If any of those boxes are checked (and
Widow/Orphan Control is checked by default), some lines may be forced to the
next page. To keep absolute control of the number of lines, uncheck all the
boxes.