Any? PDF is fixed-width and is currently laid out for desktop, so bigger than any phone - though even there, you might want to use the guide side-by-side with your actual host shell to follow some instructions - and hit the same limitation on a smaller laptop screen where text wouldn't fit and you'd have to scroll.
no, it's not. pdf has multiple rendering modes and your problem is the client you are using to view it.
the reason this book being ~20 mb with 750 pages is that %99 percent of the things inside is vectoral, including the variable font that I used. While trying to find the perfect page aspect ratio and the perfect variable font width, I tried it with many different screen sizes, operating systems, dpis etc and clearly tell you that you have another problem.
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