In Finder Preferences, I have the following settings:
Also, it pays to have the Finder View menu : Show Path Bar selected.
Additionally, in your case of searching for PDF Documents, you should first have PDF Documents selected in System Preferences : Spotlight panel : Search Results.
Then you can perform a Spotlight search from either a new Finder window's search input (without ⌘+F), or from Spotlight itself:
kind:PDF
This will initially show all PDF documents in your home folder hierarchy, and by clicking the "This Mac" alternative on the Finder window's sub-toolbar, you can see all PDF on your Mac. Because you enabled "Show Path Bar" in the Finder, when you click on any PDF icon, you will see its path at the bottom of the Finder window.
The Spotlight icon from the menubar, when using the above query, will offer to “Show all in Finder...” which provides the equivalent of the “This Mac” choice from the preceding paragraph.
If you combine:
kind:PDF name:xyz
the query will find all PDF with the “xyz” string in the filename.