The example that Microsoft provides (Github) doesn't make much sense since it's printing a XAML page and not a real PDF document.
In iOS I can simple send a printable file (image, pdf, etc) to the printer and call it a day.
Why does printing a simply PDF document so complicated in UWP? No wonder no one supports this excuse of a frame work.
Don't link me this question since it doesn't work in UWP.