Feature Description

In short: allow external renderers to output PDF, automatically display it using pdf.js.
Use case: PowerPoint (pptx) files cannot be easily converted to HTML, however, they can be quality printed to PDF.
Printing files of a custom format to PDF may be a good alternative to a lossy conversion to HTML for some other formats too.
I thought about working around this by outputting <iframe ... src=".../viewer.html?file=..."> from a renderer, but it's a hack.