This is a big achievement, congrats! A lot of time must have been put into this I am sure. And you are also making a spreadsheet product AND a PDF (preview?) product? How do you combine it?
With this and node-canvas, you have everything you need to generate PDFs. I'll add an example to the examples/ directory for that. The spreadsheet library and PDFs I talked about in OP were examples of how we use this in our application, but are closed-source.