Turnitin (TII) has some issues accepting non-text PDF files. These issues can be circumvented by adding enough text into the document to keep Turnitin happy. TII requires a minimum of 25 words in any document. Dynamics and tempo markings do not appear to count as words, unfortunately. The easiest way to take care of that is to create a cover page.
Please follow this link to the Finale online Handbook to discover how to create a cover page:
Creating a Finale Cover Page
When you are finished, simply create your PDF in Finale, and then Turnitin should accept your document.
To create a PDF in Finale see:
Creating a PDF File in Finale
To Combine your PDF files:
Now you have your combined document!