If all of your pages are the same size, you can use the Document Setup menu (File > Document Setup). Depending upon how large your document is, you may wish to turn on and experiement with the Layout Adjustment tool which is now found on the Liquid Layout flyout menu (Window > Interactive > Liquid Layout). This attempts to adjust page elements to fit the new page size.
By the way, I'm assuming you're using CS6...
I hope that helps.
If you don't mind having the text reflow (and the images possibly changing sizes as well) this might work. layout adjustment depends on objects being sanped to guides, though, so results are not always predictable.
You can also consider placing these pages into a new document with the correct page size. Using that method all editing must be done in the original, but the entore page can be sacled without changing any realtionships between the elements.
As DOD and Peter have suggested, Layout Adjustment is probably the way to go. You will have to do some manual adjustments, but this tool can help save you some time.
If you are using CS5 or earlier this explains the process:
For CS6 you can use the Liquid Layout menu to do this: