Alos, the point of working with HTML is to let the app users to modify directly their report in the HTML and then still be able to download the PDF.
Think about an invoicing tool. You could have the invoice in HTML with some kind of rela pdf look.. users could for example delete rows, change amounts, ... and still be able to download the invoice in PDF just after.
This is our first attempt to make a video. It shows the path we took in order to create web applications using Erlang and Mochiweb. Your feedback is more than welcome.