pdflatex can't compile

[elben10]

Rstudio says "Fatal fontspec error: "cannot-use-pdftex"", when I try to knit the document. Are there anyone who can explain why it says that?

[svmiller]

My hunch is you'll need to update pdftex. You'll need texlive 2015 at the oldest because I use pdftex to compile with a fontawesome package. Failing that, you should be able to turn off fontawesome in the preamble to get a PDF.