XFind is an osax for Mac OS X (10.4 aka Tiger), this is a little replacement to the broken ’find’ command of the Finder.
The search window of the Finder is very basi, it does not allow to use serach patterns such as "*.png", however :
To search a file whose name is foobar or contains the word foobar and is of kind PDf then you should do :
spotlight find "foobar kind:pdf"
Or le whose name is foobar or contains the word foobar and is of kind PDF and was accessed yesterday :
spotlight find "foobar kind:pdf date:yesterday"
For a full list of the supported keywords : Spotlight tips