The PdfRenderer plugin doesn't work with EPiServerBlobReader. The regexes only include image file extensions, so the reader ignores PDF files. As the ToDos suggest, ideally the list of supported file extensions should not be hard-coded but would instead be acquired from the plugins that ImageResizer has loaded at the time. I think you can get those using ImageResizer.Configuration.Config.Current.Pipeline.AcceptedImageExtensions.
The PdfRenderer plugin doesn't work with EPiServerBlobReader. The regexes only include image file extensions, so the reader ignores PDF files. As the ToDos suggest, ideally the list of supported file extensions should not be hard-coded but would instead be acquired from the plugins that ImageResizer has loaded at the time. I think you can get those using ImageResizer.Configuration.Config.Current.Pipeline.AcceptedImageExtensions.