To explain a bit, (but ignoring many gory details), a PDF knockout
group can be a very complicated thing, so poppler has some fairly
sophisticated code to handle these. This support involves rendering
-everything in the group twice and then using cairo's DEST_OUT and ADD
+everything in the group twice and then using cairo's `DEST_OUT` and `ADD`
compositing operators to properly combine them. Well, PostScript can't
-do fancy compositing like DEST_OUT and ADD, so of course cairo falls
+do fancy compositing like `DEST_OUT` and `ADD`, so of course cairo falls
back to image-based rendering for things. The irony here is that the
only reason cairo is using a knockout group in the original PDF file
is to _prevent_ any compositing from happening, (the fallback image