Sorry, this section is under construction. These terminals find and access fonts using the external fontconfig tool set. Please see the fontconfig user manual. It is usually sufficient in gnuplot to request a font by a generic name and size, letting fontconfig substitute a similar font if necessary. The following will probably all work:
set term pdfcairo font "sans,12"
set term pdfcairo font "Times,12"
set term pdfcairo font "Times-New-Roman,12"