Do not use random PDF sites. The Megathread points to Anna’s Archive and Z-Library (active links) . These are the only reliable sources for academic textbooks right now.
The keyword includes "free," which is crucial. The Megathread does not host any pirated files itself. Instead, it provides a list of trusted links—indexes of free content. These include: megathread r piracy free
In short, the Megathread is a "Yellow Pages" for digital freebies. It exists because the Reddit community realized that 90% of piracy websites are scams, and they wanted a single, safe list. Do not use random PDF sites
Google actively de-lists the r/Piracy Megathread. If you search for it directly on Google, you will likely see the subreddit itself, but the direct link to the wiki page is often hidden or "soft-blocked." You must navigate to it via the subreddit’s front page. In short, the Megathread is a "Yellow Pages"
Pro Tip: If you cannot see the Megathread, it is likely because your Reddit app is set to "Card view" and the wiki tab is hidden. Switch to desktop mode or look for a pinned "Monthly General Discussion" thread—the top comment almost always contains a fresh link to the Megathread.