There is no reasonable way to do this. The only conversion of PDFs that makes sense in the general case is to rasterize them to images of some arbitrary DPI. Then, you could simply insert these images into an HTML document.
This is more-or-less what we do in our application when we want to present a PDF for review or perform drawing on top of PDFs in contexts where we cannot rely on PDF libraries for whatever reason.
This is more-or-less what we do in our application when we want to present a PDF for review or perform drawing on top of PDFs in contexts where we cannot rely on PDF libraries for whatever reason.