It depends what the PDF is. Reading a PDF book is tedious because you're endlessly panning back and forth at every line. But you don't read a restaurant menu from start to finish like that so it makes sense to have a less linear way of navigating than scrolling.

> Scrolling itself isn't tedious compared to panning and zooming a PDF.

I simply disagree, and think the EXACT opposite.

Panning and Zooming a two-dimensional, immutable file itself isn't tedious compared to scrolling.

(You're straw-manning PDFs, though it could be any 2D image or mutable document file)