Stretch (or Shrink) to Fit
When the image won't fit the page, use Content-Aware Scale to resize the background. And if you're working with a human subject, click the Protect Skin Tones icon in the Options Bar, it will even leave the subject itself untouched. Press-ing Command-Option-Shift-C (PC: Ctrl-Alt-Shift-C) gets you there.
This must be in CS4 because I dont see Content-Aware in my menu’s ….. Stating what version of photoshop would be helpful.