With PDF, my best approach was to go very low level. I've used PDFKit and PDFBox libraries and both provide a way to output vector operations. It allows to implement extremely performant code. The resulting PDF is tiny and looks gorgeous (because it's vector). And you can implement anything. Code will be verbose, but it's worth it.

I even think that it's viable to output PDF without any libraries. I've investigated that format a bit and it doesn't seem too complicated, at least for relatively dumb output.