I was able to do this successfully. The issue that I am facing now that while merging 4 forms together.. if the 2nd or 3rd form happens to be in Landscape orientation, all rest of the forms also convert to the Landscape orientation. Also, when I try printing it, the Printer says the Printer Size did not match Paper type or something of that sort. Following was my DDX:
<DDX xmlns="http://ns.adobe.com/DDX/1.0/">
<XDP result="MyXDPResult">
<XDP source="sourceXDP1"/>
<XDP source="sourceXDP2"/>
<XDP source="sourceXDP3"/>
<XDP source="sourceXDP4"/>
</XDP>
<?ddx-source-hint name="sourceXDP1"?>
<?ddx-source-hint name="sourceXDP2"?>
<?ddx-source-hint name="sourceXDP3"?>
</DDX>
North America
Europe, Middle East and Africa
Asia Pacific