We know we don’t yet have a differ that supports PDFs, so we should not request diffs for them (because they’ll always appear broken). Instead, we should:

• Show each PDF side-by-side for “Side-by-Side Rendered”
• Show the new PDF for “Highlighted Rendered”
• Disable all other diff types

Does that seem right? Or should we just show alternate options altogether for types that we know we can’t diff? (e.g. “Side by Side,” “Before,” and “After”)

We could also definitely do better on surfacing mime types in source_metadata. Or maybe make it an actual, top-level field on version objects (any thoughts there, @dallan?).