You expect that some companies are publishing a parts catalog in PDF format?
The query just seems odds to me, and so the garbage results don't seem too surprising
You could always find a parts catalog, service manual, that sort of thing scanned and posted online. PDF (used to) select for the scanned documents. Used to be my main usage of google was finding service manuals for auto and electronics.
Nowadays the spam just pretends to be a pdf cause we used to always search for them.
It's really common in some areas. This at least used to be a very effective search pattern.
Don't them all? Once you get to niche products, there are even web stores out there that only list their parts in PDF.