Then resize your document.
This only really works if you've consistently aligned objects on the page to guides.
Just did a quick test in IDCC.
Layout>Alternate Page Layout
In the text box select the page size to adjust to and and use Scale in Liquid Page rule drop down, this will get everything scaled up or down to fit on your new page size but it ignores margins and guides. There are other settings to experiment with in the Create Alternate Layout dialog probably trial and error until you find what works for your application.
This creates a second layout in your existing document.
To adjust existing document try layout>liquid Layout scale then use the page tool Shift+p you can drag corners to preview for pennant change to take place use Alt+drag