An on device, native, normal regular Adobe PDF reader just like every other (smart) mobile device already has; when I moved from Nokia S60 to BlackBerry I couldn't believe how lacking the devices were for people to read PDFs off the SD card, it's horrible.

(not some server based solution, not email, not some hacky "let's make GIFs", not a payware - a free, normal Adobe PDF reader. that's it, nothing more)