Help!! Chuck
When I first did File > Print > Setup... ,I clicked on the Setup button at the lower right. This brought up the message
"If the desired print setting is available in InDesign's Print dialog box, please set it there to avoid printing conflicts"
I ignored the message and proceeded to select my printer and enter its setup properties before returning to the InDesign Print dialog. One of the properties I had set was document size=75%. That was the problem.
Note that the InDesign Print continued to show scale=100%!!
Chuck