Although the end-problem that this would solve is a TeX one (installing a new font for PDF output), this particular solution that I'm looking for is a Sphinx issue. Sphinx uses standard LaTeX when making PDFs, which is fine so far, but I need to install a new font and have tried and failed. I understand this is a far easier process using XeLateX, so would like to know if there is an extension or some way to configure Sphinx to make it use the XeLaTeX builder instead.