There is no functional differences in full and demo versions except the demo version watermarks the resulting documents.

In general the tag should work. But:
– HTTPS is not supported if PD4ML is deployed to Weblogic or WebSphere, as the application servers implement proprietary SSL level, not derived from Java’s SSL implementation. Solution: to implement a custom resource loader, utilizes platform specific SSL classes. Or even better – use HTTP instead of HTTPS.

– Make sure the valid path is valid not only from browser, but also from the server where PD4ML deployed to. A usual situation: the server cannot resolve host name etc. Try to enable PD4ML debug output and inspect server’s log for errors.