bagging a pdf in Chrome gives a useless saved page

I tried to bag a pdf I had loaded in Chrome (an https url - https://www.cse.chalmers.se/~rjmh/Papers/arrows.pdf), and all it saves is a blank page with the url. In wallabag I see title=file name and the correct url, but no contents.

More broadly bagging pdfs is broken in wallabag too, as when I copy/paste the pdf into wallabag.it it ends up saving gibberish - likely the raw bytes of the pdf. I was hoping I could use wallabag to read pdfs as well as html but that's not looking feasible.