"You write in plain text or human-friendly CommonMark"
"DocGen styles and publishes all your content as a website"
"DocGen also creates an equivalent PDF copy"
DocGen is probably not the right tool for precision PDF layout. Or for product configurators which need to output variants based on a common template. Docgen is intended more for free-form, human generated content which is regularly updated and refactored, and standardised for each product release.
sudo npm install -g docgen-tool docgen scaffold docgen run -o $HOME/docgen-example
See the installation guide for more detailed instructions.