Export to PNG file formats requires the LibRSVG (SVG rendering) library or Inkscape to be installed.
Export to PDF requires LibRSVG, Inkscape or webkitToPDF to be installed.
brew install librsvg
sudo apt-get install librsvg2-dev
To install, download the latest binary file from the releases page, and move the application into your PATH. For example, after downloading and unzipping the application, use the following command to install the program (requires the administrator password):
sudo mv webkitToPDF /usr/bin