print dialog page size
Since the latest version, the print dialog box no longer clearly shows when the image area exceeds the page size on the preview in the lower left. Before, the image area that would not print would be greyed. That is no longer the case.
Please update InDesign to the latest version, InDesign CC 2018 (13.0) for the fix of the issue.
We have fixed this issue in our Beta build. You can test and try the fix in the Beta build posted on the InDesign Pre-Release program. Follow the below link for joining InDesign Pre-Release program and getting access to the Beta build of InDesign.