[tomsem]

Both Paperwhite and Kindle Touch have a 'column reading' mode, which you enter by double-tapping the text you want to start with. In this mode, it will stay zoomed in and fit the current column to the screen width. Page turn gestures then will advance to the bottom of the column, then to the next column (or page). It will stay in this mode until you double tap again. It will work with single column page layouts as well.

It doesn't work perfectly (column detection is heuristic, not based on the structure of the PDF document, since that can be horrible), but it is much easier than manually zooming and panning around.

The other thing that is often workable is to go to landscape mode (the above column mode is available there as well, useful in single column to trim white space).

Sony has some interesting PDF navigation options as well but at least on the PRS-T1 they messed up landscape mode. I can never get optimal fit to screen, and the cropping tool is broken.

That said, everything is much better for PDF on a 9-10" tablet. Better apps and with better PDF support.