Hi Sushmitha,
This question may help validate that you are setting up the widget correctly
https://forum.mendix.com/link/questions/87822
edit:
in order to display your pdf in mendix, you have to store in an entity that is a generalization of the system.filedocument entity. Once you have this object that is a generalization of filedocument. Pass that to a page that has a dataview of the entity thats holding the pdf and then put the document widget into it