A DSL designed for PDF creation is a much better way to approach this. It gives you way more control over what you're doing. Concerning pdfkit specifically, I think a JSON file is a gruesome way to design a PDF, but IMO it's still better than converting from HTML unless you're doing something very simple.
If someone (Apple or Google) would get wise and implement the full paged media spec then PhantomJS/wkhtmltopdf/your browser might be a viable option for full fidelity print output.
Until then our apps will have to suffer with one layout language for viewing (HTML) and have another for print like this lib.
Simpler as in ease of use? Well that's subjective, some might find HTML easier than learning a new layout model, other might like something more focused on just PDF layout like this.