I installed KindlePDFViewer on my Kindle DX White and I'm very pleased with portrait fit-to-width cropping and with gamma correction (by volume +/- button) that quickly and easily improves contrast (makes letters darker) for poor scans.
Maybe you should correct this line in installation instructions:
- Connect your Kindle to your PC with usb cable, and copy the file you just downloaded, kindlepdfviewer-v2012.10.zip to your Kindle in folder “customupdates”.
by adding "and unzip it in there" because it misled me at first
Is it safe to have both Duokan and KindlePDFViewer installed at the same time without any issues, by firstly installing Duokan or after by using Kite as launcher for KindlePDFViewer (no need for jailbreaking) or even after Launchpad by unistalling the jailbreak ?