Vish, a couple of things you may want to check...
--can you access http://<servername>:<port>/CAisd/pdmweb.exe
? if not, maybe the Catalina tomcat instance is not running?
--do you see the following entries in the web.xml file in SDM-install\bopcfg\www\CATALINA_BASE\webapps\CAisd\WEB-INF:
<servlet>
<servlet-name>PDMExport</servlet-name>
<servlet-class>com.ca.ServicePlus.pdmweb.PDMExport</servlet-class>
</servlet>
...
<servlet-mapping>
<servlet-name>PDMExport</servlet-name>
<url-pattern>/PDMExport</url-pattern>
</servlet-mapping>
...
if not, you would need to run pdm_configure to add the servlet into the Catalina Tomcat configuration
--Like Mike mentioned here, do you have NX_SERVLET_SERVER_URL and NX_LOCAL_SERVLET_SERVER_URL
in NX.env set properly? if not, you would need to set them right and recycle sdm
Hope one of these hopes. Thanks _Chi