I just went through this whole hunt last week, so I can save you some time. Searching for a PDF preview of 'In the Blink of an Eye' is tricky because the title's pretty common. There's a novel by Walter Murch about film editing and a newer one by the same title by Maureen Joyce Connolly, I think? Amazon's Kindle store usually has the 'Look Inside' feature for most books, which gives you a decent chunk of the first chapter. That's where I started.
Honestly, I'd skip the wild web for a PDF sample. It's either a full, questionable download on some forum (which isn't cool) or a broken link. Your best, legit bet is to check the retailer page for the specific edition you want—Apple Books, Google Play Books, and Kobo all have preview systems too. I find the sample length varies; sometimes it's generous, sometimes it cuts off right before things get good, which is its own kind of agony.
For the Murch book, I remember the preview gave a solid sense of his technical but accessible style, enough to know if I wanted to dive into film theory.