PDF mode as expected has some challenges.
I took one of my technical documents. By default I got a 98% zoom and clearly small text. There is no sense wasting my time here so I switched to landscape.
Notice the page number "5 of 27" as expected. This time I got 131% zoom, which is better. Also margins are not as big, but still there. There is a small icon at the bottom indicating additional page content below. I found the text to be readable, but fairly small. I had to keep the reader close. Also the lack of font manipulation options means that you have very limited options - in essence only 2 zoom levels.
On the other hand this mode offers more view customization: portrait/landscape plus flipped. Between them you can get any orientation you like. In effect you can move the buttons to any corner as you like! I wonder why TXT mode lacks these options. Conversly PDF mode lacks bookmarks from the TXT mode. I guess it was a last minute addition and they didn't have the time to do it in PDF mode. Still I hope it will be added to this mode as well.
"Fit xxxx" commands should be familiar to anyone who used PDF files.