The command \linespread{factor}
is supposed to multiply
the current \baselineskip
by ‹factor›; but, to all
appearances, it doesn't.
In fact, the command is equivalent to
\renewcommand{
\baselinestretch}{factor}
: written that
way, it somehow feels less surprising that the effect isn't immediate.
The \baselinestretch
factor is only used when a font is selected;
a mere change of \baselinestretch
doesn't change the font, any
more than does the command
\fontsize{size}{baselineskip}
- you have to follow
either command with \selectfont
. So:
\fontsize{10}{12}% \selectfont
or:
\linespread{1.2}% \selectfont
Of course, a package such as setspace, whose job is to manage the baseline, will deal with all this stuff - see “managing double-spaced documents”. If you want to avoid setspace, beware the behaviour of linespread changes within a paragraph: read “`\baselineskip` is a paragraph parameter”.