When I run the executable \"wkhtmltopdf-amd64\" (from Linux), I get the following output:
QPainter::begin(): Returned false============================] 100%
make sure you have access to the directory ie : you are the owner and have write permissions when you run wkhtmltopdf http://www.google.com test.pdf
you can always su sudo and try it out but generally i wouldn't write to any where but home just so i dont store junk in important places.