Not sure which PDF facility within MuseScore you are talking about. There is nothing built in to MuseScore itself. But the musescore.com score sharing site *does* incorporate a PDF conversion facility, powered by Audiveris, the open source PDF-to-MusicXML converter. it works reaosnably well, if your expections are set appropriately low. You have to realize this an extremely complex problem; much much harder than simply character recognition. But for sufficiently simple scores, it should give you a reasonable starting point.
PDFtoMusic is a compact Windows application built specifically for helping users convert PDF score files into music. It boasts a clean and intuitive layout that allows you to set up the dedicated.