I used an iPhone 5 borrowed from the office as a ~sacrificial~ test device for a while recently. I didn't try reading PDFs on it. For general use, it was fine, with two drawbacks:

  • squinting, because I was reluctant to bump the font size up on such a small device; mostly an issue with web pages
  • typing, especially passwords

My personal phone is a 6 Plus. Being able to read PDFs without constantly having to slide the viewing window around has been wonderful.

It seems I have both big pockets and big hands, so this phone has ended up more usable for me than a smaller one - I can hold it one-handed and still reach every point on the screen with my thumb, and it's a lot easier to avoid typos thanks to the larger keyboard. Unlike an iPad or laptop, I can pocket it and retrieve it in a jiff, so I have it with me all the time.

I could go a bit bigger, but I noticed I lost full-screen one-handed reachability with some of the largest Android phones. I find that's what dictates the cutoff in size for me.

// @kdfrawg