matical empty set, write:
        </p>
<pre class="code">&lt;fo:inline font-family="Symbol"&gt;&amp;#x2205;&lt;/fo:inline&gt;</pre>
<p>
          The "#" shows up if the selected font does not define a glyph for the
          required character, for example if you try:
        </p>
<pre class="code">&lt;fo:inline font-family="Helvetica"&gt;&amp;#x2205;&lt;/fo:inline&gt;</pre>
</div>
<a name="N104DD"></a><a name="pdf-postprocess"></a>
<h5>6.3. What tools are available for post-processing my PDF document?<spa