Is there no way to do something similar in InDesign without having to purchase a script?
Have a look at the Page tool (Shift + P).
Search the InDesign forum for "resize document" -- there are a lot of threads about this. Basically you can:
1. Print to PDF at a scaled size, or
2. Use the "Scale" option of liquid layout, or
3. Select all objects on each page and ctrl-shift-click-drag to scale them to the required size, or
4. Place the original InDesign document into another InDesign document at a scaled size.
You'll learn a lot about InDesign -- it's features and limitations -- by trying each of the above methods. Whether any are satisfactory I'm not sure.
But if it's time-efficiency you're after, my first answer applies :-)