Finding the PDF of 'Reaper' entirely for free within legal boundaries can be a real puzzle, because it almost always isn't available that way. Most major retailers and the author's own site sell the ebook. The big platforms like Amazon, Kobo, and Google Books have it for purchase, and sometimes you can 'borrow' it through services like Kindle Unlimited if you have a subscription, but that's not a permanent download.
Public libraries are the absolute champion for legal, free downloads. If your library uses Libby or OverDrive, you can check out the ebook for a few weeks. The file is DRM-protected and expires, but it's a proper, free read. The catch is availability—you might be on a waitlist. I've had some luck checking the author's newsletter or social media for occasional promotional excerpts, but that's usually just a sample chapter, not the full thing.
Honestly, expecting the full novel as a free PDF from an official source for a popular title is setting yourself up for disappointment; those files are usually found on piracy sites, which isn't what you're asking for. Your best legal shot is definitely your local library's digital collection.