PDFtoMusic Pro for Mac

From Myriad Software:

PDFtoMusic gives you full access at last to the huge PDF music score collection available on the Internet. If you wish to go further, with Melody Assistant or Harmony Assistant, you'll be able to alter the score, remove parts, transpose them, or completely rearrange the whole piece. The "Pro" version of PDFtoMusic also enables to export the result in MusicXML format, which is managed by most of the professional score editors, as well as tune up finely the calculation settings. Considering that creating a PDF file from any program (even old or discontinued products) is a breeze, PDFtoMusic Pro then becomes the ideal bridge between your miscellaneous score editors.