InDesign does have a scale function, accessed via the Liquid Layout tools. It's kind of clunky and unreliable, but you can give it a shot.
A much simpler and more reliable alternative is our QuickResize add-on: http://www.id-extras.com/products/quickresize
Both options will also change the page size, I believe, but after the document has been resized, it's easy enough to change the page size back to what you want: File>Document Setup.