I believe that TREX is the tool that will perform the indexing, but you need the Enterprise Search system to tell TREX how to do it/set it up correctly.
https://help.sap.com/saphelp_nwes73/helpdata/en/4a/654f39cd241c50e10000000a42189c/content.htm
I didn't come across anything specific like PDFs, but I would also assume this falls under the meta data type of terminology.