When I have PDFs that are improperly sized for my reader, I've had by far the most luck with tools that either modify, or rasterize and then modify the PDF rather than converting to some
other text based format: between
soPDF,
PDFLRF,
PaperCrop,
Rasterfarian and
PDFread, I can usually make any PDF fit on my 505, even highly technical journal articles. But these tools work in a very different way, preserving the exact look of the PDF but cutting it up.
Heck even if my target device were a kindle, I'd seriously consider using PDFLRF and then convert the LRF to mobi afterwards.