I assume this isn't a deliberate strategy and is instead a result of an automated system with almost no human supervision. If it just crawls the web looking for

I assume this isn't a deliberate strategy and is instead a result of an automated system with almost no human supervision. If it just crawls the web looking for PDFs, it won't be able to distinguish between legitimate and pirate copies. This kind of unsupervised automation is typical of Amazon and other tech companies.