When I read pdf's with the adobe reader I almost always do it in portrait mode with black bars on the left and right sides. I can change (with adobe reader) how pc screen real estate is used, or I can zoom the fonts and reflow as described above.
On the kindle its reader attempts to use all screen real estate all the time. Unless the pdf was created with the KDX in mind, you don't get very readable results.
You are right that the zoom as implemented by Amazon isn't all that useful (except perhaps for blowing up complex diagrams, figures, or pictures). Read on the DX in landscape mode is a little better save that there isn't very much text on each page, and paging forwards and backwards pdf's while in landscape mode is very much slower than the same operation in portrait mode.
Your thought about two column texts are not particularly valid (in my experience with same on the DX) as the zoom percentages (150, 200, 300%) seem more suited to the non-DX kindles. At any rate with two column texts, and zoom, you need to pan a lot to the other column -- also with the fixed zoom percentages, and the non-continuous pan movements possible, it is often not possible to set a kindle dx up in a way to make reading two-column texts practical/pleasing (ie able to read without a lot of back and forth panning)
My experiences have been with a lot of pdf's from a variety of store-bought and self-created sources on a KDX US. I have zero experience with regular kindles -- perhaps zoom and pan is more usable on those smaller devices.
I only hope that Amazon soon comes out with a more useful PDF reading capability either on existing, or new devices.
As currently implemented the kindles do not handle pdf's well enough to deal with long reading sessions of the textbooks/technical books where pdf's make the most sense.
Amazon needs a pdf reader at least as good as Adobe's -- the current kindle processors, however, may not be fast enough to support such a reader.
Last edited by eboyhan; 07-11-2010 at 12:43 AM.