[fjtorres]

The commercial pdf converters from Nuance and AbbeySoft (among others) convert pdfs to useful formats by printing to pages to memory and OCRing the image to recreate the original text stream.
One way to test the functionality of the PB360 pdf viewers is to take a text-based document (rtf, doc, html) with and without pictures, format it to your liking, and "print" it to a pdf file using the default settings. Then repeat the exercise setting the output page size to 3in by 4in and 4.5in by 6in. You may have to go back and adjust the text document formatting (font size, margins, line spacing) to get something suitable for a small screen.
You can use this same approach to convert your text only pdfs.
You should also take a look at the free creator app from mobipocket.com; it converts pdfs to mobi format and in the process it drops a very clean html document in the conversion directory. Just make sure to install it in professional version to get the pdf input version.

What is going on is that the PB readers support 3 different breeds of files: ebook files (epub, mobi, fb2) that (generally) convey book structure and formatting; electronic document files (rtf, doc, txt, html) that only convey content and formatting, to varying degrees; and electronic paper files (pdf, djvu) that mostly convey the appearance of the original sheet of paper for archival purposes. Which is why some pdfs behave as digital microfiche and only offer zoom and panning options, the file was only intended to be viewed as a printout.

The rule of thumb is that pdfs are best viewed on paper. Anything else, even big color screens, is a degraded experience. Small b&w screens are just about the least suitable vehicle for viewing pdfs. Sorry.

Hopefully you can find a way to convert your files to something useful.