The HP comes with its own CompactFlash card slot, so it would only be a matter of transferring the card from the Newton to the PC. Also, from what I have read, the Newton OS is compatible with Windows. Naturally, I would have used a Mac, but I do not know of any Mac that had a PC card slot built-in (The MBPs use to have an ExpressCard slot, but I think that's a different breed of card altogether).
A program like WordPerfect or WordPad should work.