When you click on an image in InDesign and review the Link Info. in the Links panel, there is the Actual PPI and Effective PPI information. I understand InDesign will pull the data embedded in the Photoshop file. But what settings panel/menu from within InDesign governs how InDesign reads the PPI data and can it be adjusted?
And perhaps my second question is related to the first one above, when you package a file, how can you tell InDesign to flag any images that do not meet a specific PPI outside the pre-existing default settings?
But what settings panel/menu from within InDesign governs how InDesign reads the PPI data and can it be adjusted?
ID resizes images, it doesn't do any resampling except when you export to PDF—on export you have the option sample down but not up.
When you scale an image it's the same as resizing in Photoshop (unchecking the Resample Image box), so actual and effective ppi are the same when the scale is 100%, if the scale is 50% the effective ppi is 2x higher and that will be reflected in the output.
You can use preflight to check output or effective resolution.