I have a children's book ready for the publisher in all ways but one—I cannot for the life of me seem to figure out how to get the requisite 3 mm gutter in between the pages of my spreads. Though the file is ssent off in page-only form, it is designed in spread format because the illustrations cross both pages. The publisher doesn't want ink in the gutter to get in the way of gluing. I had tried making each page a single column and entering a gutter, but that was apparently not it. What can I do?
You're doing everthing correct by setting up your file as spreads. The printer should take care of the gutter when they impose your file. When exporting a PDF or printing from INDD, they should set the inside document bleed settings to 0 and make the gutter whatever they want in their impostion software.