Hi all, I know this thread is old af but I just figured out how to make the nPDF work and since I strugled a bit to install it I just decided to make a reply.
Idk if its the same for all but the file found in the download link does not work when put on the calculator, when opening a pdf it just keeps on giving the error "file.pdf.tns is not supported".
I found this other link with all the files in order:

https://github.com/Legimet/nPDF/releases

hope it helps anyone in the future!