Configure the web.xml to run pipelines for .pd files:

<servlet>
    <servlet-name>PipelineEngine</servlet-name>
    <servlet-class>com.smallx.servlet.PipelineServlet</servlet-class>
       <init-param>
            <param-name>check-for-changes</param-name>
            <param-value>true</param-value>
       </init-param>
       <init-param>
            <param-name>default-pipeline</param-name>
            <param-value>request.pd</param-value>
       </init-param>
</servlet>
    
<servlet-mapping>
    <servlet-name>PipelineEngine</servlet-name>
    <url-pattern>*.pd</url-pattern>
</servlet-mapping>

This pipeline will be used for get requests and so we don't need to create an 'index.xml'.