Unable to search string Inside PDF or Doc file


I have configured a scheduler which perform lucene index for documents added.

When I add pdf file or doc, and after the indexing has rebuilt via scheduler, Search results does not return any keyword searched inside PDF or doc file.

However, It does return the result when its docx file.

I am using Suitecrm 7.3, and Lucene index and Optimize index scheduler is active and running every minutes.

Can some please help ?

Also I would like to know if there is guide available for advance open discovery search