If your source pdf has bad formatting, the other suggestions would be a good start. However, if the source is good, but just looking bad when viewed on your 505, you may want to start with a simple margin crop. I know you're on Snow Leopard (same here), but if you can get hold of a Windows machine (Bootcamp or Fusion?), then soPDF is fantastic for the cropping.
https://www.mobileread.com/forums/showthread.php?t=32066 Further in the soPDF thread are some GUI apps created for it.