Setting LaTeX docs to Palatino

LaTeX documents set text by default in the Computer Modern Roman, Computer Modern Sans Serif and Computer Modern Monospaced font families.

\documentclass[10pt]{article}

\begin{document}
   \begin{list}{ }{ }
       \item Whan that Aprille with his Shoures soote ...
       \item \textsf{Whan that Aprille with his Shoures soote ...}
       \item \texttt{Whan that Aprille with his Shoures soote ...}
   \end{list}
\end{document}

The palatino package changes all three font families.

   \documentclass[10pt]{article}
   \usepackage{palatino}

   \begin{document}
       \begin{list}{ }{ }
           \item Whan that Aprille with his Shoures soote ...
           \item \textsf{Whan that Aprille with his Shoures soote ...}
           \item \texttt{Whan that Aprille with his Shoures soote ...}
       \end{list}
   \end{document}

Prebuilt packages like palatino do not exist for all fonts.