I'm probably missing something, but it seems wasteful to convert PDFs to HTML just to convert them to images in a separate stage immediately afterward?
Someone else mentioned a way to push images directly to the display but I didn't find an API to make this work. Also using HTML allows my to inject other dynamic content, not just PDF's such as a dashboard, weather, widgets, etc. It also makes it easier to display error messages if the newspaper server is down without needing to render images for errors.
It is possible to use the HTTP backend where you manually convert PDF to images and then push images directly to the server and the device.