Re: I disagree with the article
Annoyingly, I've had a similar experience of late with Bing.
Granted I've been doing a lot of rather specific searching for old spec sheets which have been dropped from the manufacturer's website but are often still lurking on the sites of dealers and distributors.
Entering the document number (every sheet has a unique reference in the footer) plus ".pdf" frequently returns zero hits in Bing but a plethora of results on Google. DDG seems to sit somewhere in the middle.
Maybe Bing just sucks at indexing document text.