You can build a DITA-OT plug-in that contains a customized PDF transformation.

1. In the plugins directory, create a directory named com.example.print-pdf.
2. In the new com.example.print-pdf directory, create a plug-in configuration file (plugin.xml) that declares the new print-pdf transformation and its dependencies.
   Figure 1. plugin.xml file

   <?xml version='1.0' encoding='UTF-8'?>
   <plugin id="com.example.print-pdf">
     <require plugin="org.dita.pdf2"/>
     <feature extension="dita.conductor.transtype.check" value="print-pdf"/>
     <feature extension="dita.transtype.print" value="print-pdf"/>
     <feature extension="dita.conductor.target.relative" file="integrator.xml"/>
   </plugin>

3. Add an Ant script (integrator.xml) to define the transformation type.
   Figure 2. integrator.xml file

   <?xml version='1.0' encoding='UTF-8'?>
   <project name="com.example.print-pdf">
     <target name="dita2print-pdf.init">
       <property name="customization.dir" location="${dita.plugin.com.example.print-pdf.dir}/cfg"/>
     </target>
     <target name="dita2print-pdf" depends="dita2print-pdf.init, dita2pdf2"/>
   </project>

4. In the new plug-in directory, add a cfg/catalog.xml file that specifies the custom XSLT style sheets.
   Figure 3. cfg/catalog.xml file

   <?xml version="1.0" encoding="UTF-8"?>
   <catalog prefer="system" xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
     <uri name="cfg:fo/attrs/custom.xsl" uri="fo/attrs/custom.xsl"/>
     <uri name="cfg:fo/xsl/custom.xsl" uri="fo/xsl/custom.xsl"/>
   </catalog>

5. Create the cfg/fo/attrs/custom.xsl file, and add attribute and variable overrides to it.
   For example, add the content highlighted with bold to change the page size to A4.

   Figure 4. cfg/fo/attrs/custom.xsl file

   <?xml version="1.0" encoding="UTF-8"?>
   <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                   version="2.0">
     <!-- Change page size to A4 -->
     <xsl:variable name="page-width">210mm</xsl:variable>
     <xsl:variable name="page-height">297mm</xsl:variable>
   </xsl:stylesheet>

6. Create the cfg/fo/xsl/custom.xsl file, and add XSLT overrides to it.
   For example, the following code changes the rendering of <figure> elements.

   Figure 5. cfg/fo/xsl/custom.xsl file

   <?xml version="1.0" encoding="UTF-8"?>
   <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                   xmlns:xs="http://www.w3.org/2001/XMLSchema"
                   xmlns:fo="http://www.w3.org/1999/XSL/Format"
                   version="2.0">
     <!-- Move figure title to top and description to bottom -->
     <xsl:template match="*[contains(@class,' topic/fig ')]">
       <fo:block xsl:use-attribute-sets="fig">
         <xsl:call-template name="commonattributes"/>
         <xsl:if test="not(@id)">
           <xsl:attribute name="id">
             <xsl:call-template name="get-id"/>
           </xsl:attribute>
         </xsl:if>
         <xsl:apply-templates select="*[contains(@class,' topic/title ')]"/>
         <xsl:apply-templates select="*[not(contains(@class,' topic/title ') or contains(@class,' topic/desc '))]"/>
         <xsl:apply-templates select="*[contains(@class,' topic/desc ')]"/>
       </fo:block>
     </xsl:template>
   </xsl:stylesheet>

7. Create an English-language variable-definition file (cfg/common/vars/en.xml) and make any necessary modifications to it.
   For example, the following code removes the period after the number for an ordered-list item; it also specifies that the bullet for an unordered list item should be an em dash.

   Figure 6. cfg/common/vars/en.xml file

   <?xml version="1.0" encoding="UTF-8"?>
   <vars xmlns="http://www.idiominc.com/opentopic/vars">
     <!-- Remove dot from list number -->
     <variable id="Ordered List Number"><param ref-name="number"/></variable>
     <!-- Change unordered list bullet to an em dash -->
     <variable id="Unordered List bullet">&#x2014;</variable>
   </vars>

com.example.print-pdf/
  cfg/
    common/
      vars/
        en.xml
    fo/
      attrs/
        custom.xsl
      xsl/
        custom.xsl
    catalog.xml
  integrator.xml
  plugin.xml