Changing Font Family as in LaTeX wikibook example

Question

I want to vary the font family in my document, as demonstrated in this example from the LaTeX wikibook. I built and compiled an mwe using that same code, but in the document I generated, the font does not change.

\documentclass{article}

%% wikibooks example
%% https://en.wikibooks.org/wiki/LaTeX/Fonts#cite_ref-1

\begin{document}

% Default font (\familydefault = \rmdefault = Computer Modern Roman)
Lorem ipsum dolor sit amet, consectitur adipiscing elit.

% Palatino font (ppl must be installed).
\renewcommand*\rmdefault{ppl}
Lorem ipsum dolor sit amet, consectitur adipiscing elit.

% Iwona font (iwona must be installed).
\renewcommand*\rmdefault{iwona}
Lorem ipsum dolor sit amet, consectitur adipiscing elit.

\end{document}

I saw the admonition that those fonts must be installed, but I believe they are. I got no warnings or errors during compilation; the only seemingly suspicious and related output in the log file was the following:

LaTeX Font Info:    Checking defaults for OML/cmm/m/it on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for T1/cmr/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for OT1/cmr/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for OMS/cmsy/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for OMX/cmex/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Checking defaults for U/cmr/m/n on input line 5.
LaTeX Font Info:    ... okay on input line 5.
LaTeX Font Info:    Try loading font information for OT1+iwona on input line 18
.

(/usr/local/texlive/2017/texmf-dist/tex/latex/iwona/ot1iwona.fd
File: ot1iwona.fd 2008/07/22 v0.995 font definition file for OT1/iwona (MW)
) [1

{/usr/local/texlive/2017/texmf-var/fonts/map/pdftex/updmap/pdftex.map}] (./mwe.
aux) ) 

However, that to me doesn't indicate a problem. I have tried using fonts other than those listed in the examples, with no better results. I can add \usepackage{iwona} to the prelude, and this changes the font from the default, but for the entire document. To be clear, I'm hoping to see a change in font each time I redefine rmdefault, as in the wikibooks example. Any suggestions?

Answer 1

\documentclass{article}
%\usepackage{iwona}    % it must work when correctly installed ;)
%\usepackage{palatino} % Idem
\begin{document}

% Default font 
Lorem ipsum dolor sit amet, consectitur adipiscing elit.

% Palatino font (ppl must be installed).
{\fontfamily{ppl}\selectfont 
Lorem ipsum dolor sit amet, consectitur adipiscing elit.}

% Iwona font (iwona must be installed).
{\fontfamily{iwona}\selectfont 
Lorem ipsum dolor sit amet, consectitur adipiscing elit.}

% default again
Lorem ipsum dolor sit amet, consectitur adipiscing elit.

\end{document}

Answer 2

The Wikibook page glosses over several points, the main of which is that

\renewcommand{\rmdefault}{family}

command should be issued in the document preamble. After all, there should be just one default font family in a document.

The other main point it glosses over is that generally no user will ever do that setting, but load a suitable package for the font. For instance, if one wants Palatino, the package mathpazo used to be recommended, rather than \usepackage{palatino}, because the former also sets up suitable math fonts. It also provides the sc option that loads a “true” small caps font. For Palatino there's also the combination

\usepackage{newpxtext}
\usepackage{newpxmath}

(the second one accepts various options, look for texdoc newpx on your system or at http://texdoc.net).

For Iwona, do \usepackage{iwona}, which not only sets \rmdefault.

There are scores of font packages in TeX Live/MiKTeX nowadays, several of them accompanied by matching math fonts.