If you try to access the Google Quality Raters Guidelines PDF document, you will be out of luck. The PDF seems to have been removed from Google's servers. This happened before and when that happened it was a mistake, Google fixed it. This time, I suspect it is almost a mistake and Google will fix it.

If you try to access the PDF by going directly to it over here or just Googling it and clicking on the result [Google Quality Raters Guidelines] it will currently 404 for you.

Again, I assume it will come back soon but if not, you can get an archived version over here or at the Wayback Machine.

Forum discussion at Twitter.

Update: There is a URL on Google's server that works, at the ratershub over here.

Update 2: Danny Sullivan from Google said he will work on getting the redirect up to the right place, but it was moved:

BTW, you'll note the new location itself redirects. But our planned need permanent(ish as much as anything is permanent) address is https://t.co/zYWlkrzhps -- use that, and you're good going forward. And sorry on not having the redirect up yet. — Danny Sullivan (@dannysullivan) July 30, 2019

Update 3: Google has redirected some (not all) of the PDFs to the new location.