Hello Mr Lucky
I just found your post, and I am wondering you got any solution to your problem...I think I am going through same problem with you....
I am using a music score maker App called Symphony pro, and the app only exports the document to PDF.... When I open the PDF created by Symphony app with Affinity, it shows that there is missing font called Bravura, and all 8th notes's flag becomes squares. I tried to install the font, but it failed.
I understand I can use Preview and export the file to PNG etc, but it will be so much easier and flexible to add and change things if Affinity works.
Please advise..
Thanks!!