The article talks about wkhtmltopdf; in fact, they developed their server in response to its limitations:
The wkhtmltopdf utility has been around awhile and works great when you get it working correctly on your platform. However, the newest version as of this writing 0.12.5 has a bug prevening TOC generation on some platforms. Some Linux platforms require the installation of Microsoft font packs, and compiling from source leads you down a rabbit hole of dependency hell.
https://wkhtmltopdf.org/