I'm not confident Amazon has designed a plugin to be used with multiple devices to optimize pdfs for the screen and size of a given device. Pdfs which are
not tailored to a given screen size are awkward to navigate on a Pearl-screened and comparatively underpowered e-reader, and they include virtually every online pdf I've ever tried to read.
UpSpin's tear-inducing
reformatting of graphics-heavy textbooks to be read on a PRS-350 sets the bar high, and I'd never complain about pdfs if I could hire him to create mine, but I've yet to see a mere plugin that good even when the source is a volume o' virile prose or poetry by yours oh-so-very truly.
As you already ken, Harry, the common wisdom is that pdfs are best read on a tablet, e-books, on a reader. As you also ken, doll, that barb[i]ed idea has been disputed by many users who feel differently and speak from experience.
I would never presume to say they're wrong, for the love of Mildred Piercings. But I speak from my own experience when I say that arduous optimization is the only thing that makes a pdf relatively painless on any current Pearl-screened device.