If you find a current, popular RPG rulebook like Pirate Borg on there, it is 100% a pirated copy. No two ways about it. You might think, "Arr, I’m a pirate playing a pirate game. It’s thematic!"
If you literally cannot afford the $15, check your local library’s interlibrary loan or ask the Pirate Borg Discord. The community is kind. PDFCoffee is not. Pirate Borg Pdfcoffee
I see the search term hitting my blog analytics: If you find a current, popular RPG rulebook