Had a play with producing PDF files from MuseScore sheet music.
I had slightly mixed results.
Saving a file using the programme's "Save As" from the menu gives a good PDF for converting by PDFtoMusic to MusicXML format.
On the other hand, printing via external "Virtual Printer", PDFCreator also produces a PDF file that will convert to MusicXML. One of the two examples I tried produced the same "back-conversion" result as the "saved" PDF. The other one gave a slightly scrambled conversion, with two notes which should play one following the other being played simultaneously as counterpoint, and only taking the time allocated for one of them. Of course, once converted to MusicXML, the files could be re-edited by a suitable programme, but wouldn't be suitable for letting a stranger hear the tune as you intended.

As for PDFtoMusic and Noteworthy Composer. If the link provided by Guest above can give a direct and reliable conversion to MusicXML, I wouldn't bother with the PDF conversion route.

As same Guest points out, the PDFtoMusic Pro programme costs about 200 Dollars or Euros. That said, it works in Demo mode for the first page of a PDF score, so if you are dealing with short tunes, it may still get you a result without having to buy.

Quack!
GtD.