I was just looking for this myself yesterday! It’s actually a little tricky because Emily Henry’s publisher, Berkley, is pretty strict about digital distribution. The PDF specifically isn’t a format they usually sell directly to readers. Your most legitimate options are buying the ebook on major retailer sites like Amazon Kindle, Apple Books, Google Play Books, or Kobo. They all have the ePub version, which is the standard ebook file. If you’re absolutely set on a PDF, some online bookstores might offer it, but honestly, the ePub on a Kindle or Kobo app works just as well and supports the author properly. I’d steer clear of those sketchy sites offering ‘free PDF downloads’—they’re almost always pirated and kinda spoil the whole point of enjoying the book the right way.
Also, check your local library’s website! Apps like Libby or OverDrive let you borrow the ebook version for free, which is totally legal and awesome. It’s not a download you keep forever, but if you just want to read it, it’s a fantastic option. My waitlist was a few weeks, but it was worth it for a legal read.