YSK that to get higher-quality information in your searches, you can search specifically for PDF files. You do this by appending "filetype:pdf" to your query

You can even add a search like this to your browser’s inbuilt search engines, with a string like this:

https://duckduckgo.com/?q=filetype%3Apdf+%25s&ia=web

The %s is the placeholder string used by both Firefox, Chromium, and many of their derivatives like LibreWolf, ZenBrowser, and Vivaldi.