download pdf to musescore

Export only: https://musescore.org/en/handbook/3/file-formats#graphics
Import: File/Import PDF (experimental, based on Audiveris).

But don't get your hopes too high

To be clear: MuseScore opens scores in its open format. It can also import scores in the industry-standard MusicXML format. But a PDF is just a picture. There are various AI programs that can attempt to take a picture and reconstruct an actual MusicXML file from that, and then import that into MuseScvore, but as mentioned, don't get your hopes up. It's roughly equivalent to taking a picture of a cake and then asking a computer program to reconstruct the recipe.