The PDF is basically the assembled bootloader + PDF file, which starts after a few bytes. Some PDF parsers expect the %PDF header at the beginning of the file,

The PDF is basically the assembled bootloader + PDF file, which starts after a few bytes. Some PDF parsers expect the %PDF header at the beginning of the file, which explains why it does not display on Github. It does work on macOS Preview though. I'm scared of opening any downloaded file, by now ;)