We also need to generate vector PDFs serverside — so we use a node library that speaks the HTML Canvas API and can generate PDFs. This way the result is exactly the same as the rendered sheet music in the web browser. Nice!
The upshot is: this kind of library allows for code reuse in non-browser contexts.
Our graphics engine works with Canvas API instructions — like "draw a line from point (A,B) to (C,D)." This API is small enough and low-level enough that it can also generate pristine vector output.
That's in fact one of the features of Skia Canvas (vector output in PDF and SVG).
I am not sure if it would be viable to use for thousands of PDF generation per minute but it worked great. I wasted a lot of time trying to find a good lib for HTML->PDF and they all kinda sucked in different ways. The only downside is that the chrome PDF api doesn't have a way to generate a table of contents with page numbers.