PDF backend

It proves it's possible to achieve it in pure Python,

    > without requiring fonttools. And it can be a good source
    > of inspiration. Perhaps the licence is compatible with
    > matplotlib's one?

it is BSD which is compatible-- it appears that ttfonts pull in a bit
more or report lab, but this might be worth looking into. I don't
know if and how the techniques cold be generalized to PS embedding. I
think the problem Paul ran into (who did the PS embedding work) was
not getting the relevant info for specific glyphs, but how to write
the postscript to encode the subset.