First, a confession. To get this to run on my Mac, I probably installed a bunch of stuff, such as Latex. I don’t remember what I did to make it work, so you will have to reverse engineer that.
Here is the command I run to convert a Markdown document called document.md into a PDF called document.pdf:
pandoc document.md -o document.pdf --pdf-engine=xelatex -V mainfont="Arial" -V geometry:margin=1in