Add the possibility for users to override a file genereated by maven

git-svn-id: https://svn.apache.org/repos/asf/maven/maven-1/plugins/trunk@114928 13f79535-47bb-0310-9956-ffa450edef68

pdf/plugin.jelly

@@ -93,7 +93,7 @@
             </fileset>
         </copy>
         <!-- Copy all of the user-supplied xdocs -->
-        <copy todir="${docsPdf}" force="true">
+        <copy todir="${docsPdf}" force="true" overwrite="true">
             <fileset dir="${docsXdocSrc}">
                 <include name="**/*.*"/>
             </fileset>