capella-scan 8 is able to directly open PDF scores.
In the "Open Image" dialog please pay attention to the "PDF options" below: Here you can select two different methods to handle bitmaps.
Depending on how your PDF file was created one or the other option might be better for score recognition. Sometimes there are huge differences!
From the start it cannot be said which option is the right one. So please try out both when you are not satisfied with the recognition result.
Another tip: When page 1 of your PDF score is a cover sheet without notes, leave it out in the "Open Image" dialog.