For me, it's any device/app: Windows with Chrome/Firefox, Sumatra, PDXChange, iphone Safari, Mac Preview/Skim
The chapter looks identical, the first line of chapter 5 is "In the previous chapter, we covered the basics of the Linux operating" and it doesn't reflow when you change zoom on any device, as is pdf-typical, unlike your website where zooming in never loses the "A complete roadmap from Linux foundations to production-grade Kubernetes." text.
But instead of troubleshooting my case, just tell what the ideal client program that breaks the curse of PDF is! I'll even try the Acrobat monstrosity if it's the only one