Man, I saw this question and had to weigh in because the hunt for 'Sinners Consumed' drove me nuts for a bit. It's one of those indie dark romance titles that's not always on the big storefronts, which makes it tricky. A totally safe and legal route is to check the author's official website or social media—sometimes they sell PDFs directly through services like BookFunnel, which delivers right to your email. That's how I got my copy after following the author on Instagram. Another good spot is Smashwords; they host a lot of independent work and you can download multiple formats, including PDF, without any shady business.
If you're open to a subscription model, Kindle Unlimited might have it, but you'd read it in their app, not as a separate PDF. Honestly, I'd avoid any site that just offers a free PDF download immediately—those are almost always pirated copies, and you risk malware along with doing the author dirty. The official routes might cost a few bucks, but it's worth it to get it cleanly and support the writer. My file from BookFunnel opened perfectly on my tablet.