need to demonstrate PDF templates

I need to demonstrate how the PDF templates work to a potential client. Where do I go in the system to create some custom fields that can be put on a template and then can fill the fiields into a form and it fills out the pdf?

You add the custom fields in Admin / Studio, enter the module you want, then “Fields”. When done, save and deploy.

Do an Admin / Quick Repair and Rebuild (maybe not necessary, but just to be sure)

Then in Email templates editor you should be able to add the field as if it was a normal field.