Finding official digital copies of books that originated in webnovel spaces can be a real maze sometimes. For 'Until I Get You', I'd be really surprised if there was an official, purchasable PDF out there from a major publisher. Most of these stories start on platforms like Webnovel or Wattpad, and they usually keep readers locked into their own apps with coins or a subscription. They want you reading there, where they can track chapters and push microtransactions. The few times I've seen something like this get a proper ebook release, it's after it's blown up massively on the app, and even then, it's usually an EPUB on retailers like Amazon, not a downloadable PDF from the source. A PDF suggests a static file you can take anywhere, which is kind of the opposite of what serial platforms want.
You might find people sharing scanned copies or poorly formatted text dumps on sketchy sites, but those are almost definitely unofficial and often have machine-translated bits slapped together. The translation quality in those is horrendous—characters suddenly have different names halfway through, idioms make zero sense. If you care about actually following the story and not just collecting a file, sticking to the official app, even with its paywalls, is the only way to get the translation the author likely approved. The whole experience is designed around checking for daily updates anyway; having a full PDF would kinda ruin the serialized fun of it. I'd check the original platform's website for any 'e-book' store section, but I'm not holding my breath.