Export to PDF
When exporting to PDF I can only see A3, A4, Letter & Legal paper sizes in the drop-down list. On the pop-up where you specify those sizes it says you can input other sizes in the width/height (unit) but there seems to be no way to input these values.
It would be really nice if we could choose any paper size as shown in the printing module. I could of course print to PDF to get around this, but I don't know what happens with the DPI/print quality when doing it this way. I'm not sure if cups-pdf respects the true dpi from Darktable and probably screws around with the true print resolution.