Repligo:
I used Repligo in the past, but now I prefer to convert PDF files to HTML and read them with one of my favorite e-book readers (for the better or worse). Repligo looks great, but it hasn't been updated or actively supported in a while (RepliGo 2.0 for PPC was released 1.5 years ago). On my Axim X50v, I noticed that sometimes fonts in Repligo look "washed out" (even in reflow mode). Images are not shown in reflow mode which is another drawback.
Converting:
Always a scary business. But if you have to convert PDF content, I recommend
Iceni Gemini. It's not cheap ($159, gasp), but it does the best job converting difficult layouts.
There is an
older thread with good hints on how to survive the PDF nightmare.