How to shrink all contents in InDesign project on every page at once

I'm a little late to the party here, but my (not free) https://www.id-extras.com/products/quickresize/ does just that, very well.

There's a demo version to play around with to see how it works.

Hi @Mae5CAC ,

did you successfully shrink the contents on all pages like you want?

If you still struggle with the MultiPageImporter script just let us know.

It would be helpful if you show some screenshots of a facing pages spread where we see the current contents and the one after you scaled the contents. With guides and also showing frame edges.

Below the GUI of the script:

I think, that there are options enough to get what you want. If not, just let us know…

Just experiment with the script using only a few pages of the exported PDF.

Regards,
Uwe Laubender
( Adobe Community Expert )

Maybe try File > Adjust Layout ... on a copy of the file!

Of course placing scaled pages is going to reduce the size of the type which might affect readability. If you want to just make your frames smaller, make sure they are snapped to the current margins, then make a copy of the file (for safety) and use Layout > Margins and Columns ... and enable Layout Adjustment. You'll need at that point to add additiona pages and fix any overset text.

Here's an excellent overview of the subject from Creative Pro Magazine: "Resizing InDesign Layouts" that gives you your options:

https://creativepro.com/resizing-indesign-layouts/

You can place the native .indd file if you like. The multi-page importer script is ideal for this: Releases · mike-edel/ID-MultiPageImporter · GitHub 

I'm guessing someone can script this for you but I had this happen once in the past. I found the easiest way to do it was to export a PDF and place that into a new document with a graphic frame on the parent page set to scale it appropriately. Export a new PDF from there.