How to publish step file through code in windchill PDMLINK 11.1 M020

I am trying to generate the step file over the code as below.

ReferenceFactory rf = new ReferenceFactory ();
WTReference reference= (WTReference)rf.getReference("VR:wt.epm.EPMDocument:xxxxxxxxx");
EPMDocument epm =(EPMDocument)reference.getObject();
String objRef = ObjectReference.newObjectReference(epm).toString();
Publisher pub = new Publisher();
PublisherAction pa = new PublisherAction(PublisherAction.QUEUEPRIORITY, "H");
boolean result = pub.doPublish(false, true, objRef,(ConfigSpec)null,(ConfigSpec)null, true, "CodeRep", null,Publisher.EPM, pa.toString(), 1);

Publishing is working fine but not generating the step file output