Downsizing book dimensions with existing file

[joej24167550]

I have created an 11 x 8.5 Landscape book in Indesign, Can I downsize the book dimensions with the file I have or do I need to recreate it ?

[Eugene Tyson]

File>Document Setup

set your new size

there's also an option for Adjust Layout

And this might work for you but relies on the file setup to stringent setups. 

Then manually go through each page and ensure it's all ok.

But it really depends on the content, your setup, etc.