This is currently not possible. But this is work in progress in ezfind, where similar support for the relation and relation list datatypes where added (in next version, 2.1 I think). embeds in ezxml text could be added as well in a similar way.
The result is that when you search for something that exists in the embed/related object, then the object that embeds it will also show up in search results. So in your case the article will show up, and I guess that is what you want ( as letting the pdf show up on its own when user can't read it, wouldn't make sense imho ).
EDIT: The new "subattribute" feature will be extensible and documented, so it will be possible to write meta data extractors for data types like ezxmltext and others easily.
