How do you change the document font in LaTeX?

I found the solution thanks to the link in Vincent's answer.

 \renewcommand{\familydefault}{\sfdefault}

This changes the default font family to sans-serif.

As second says, most of the "design" decisions made for TeX documents are backed up by well researched usability studies, so changing them should be undertaken with care. It is, however, relatively common to replace Computer Modern with Times (also a serif face).

Try \usepackage{times}.

This article might be helpful with changing fonts.

From the article:

The commands to change font attributes are illustrated by the following example:

  \fontencoding{T1}
  \fontfamily{garamond}
  \fontseries{m}
  \fontshape{it}
  \fontsize{12}{15}
  \selectfont

This series of commands set the current font to medium weight italic garamond 12pt type with 15pt leading in the T1 encoding scheme, and the \selectfont command causes LaTeX to look in its mapping scheme for a metric corresponding to these attributes.