Don't know. Can I do this after the fact? I need to save these files (on deadline).
What is anti-aliasing and what does it do/what is it for?
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Are you seeing these lines in Acrobat? Do they seem to disappear and reappear as you zoom?
You might be seeing something called stitching. It's a display issue that usually does not effect printing. If that's it, you can often avoid them by not flattening your layers.
Turning off the "anti-aliasing artwork" in Preferences/General does remove the white line visible between tiles, but I now lose the smooth, straight edges on the shapes that make up the patterns in the tiles. Is there a way to have both?
The purpose of anti-aliasing is to improve the apparent smoothness as viewed on screen. It does not affect printed results. Illustrator's anti-aliasing has always had a problem of making adjacent object to appear to have hairlines between them.
Temporarily toggling anti-aliasing off is just a test to make sure that the unwanted artifacts are, in fact, due to on-screen anti-aliasing. If so then the file will probably print fine, and will not have the white slivers. If you have doubts, then you should have a contract proof printed before committing to an expensive press run.
Another way to verify that what you're seeing is just an artifact of on-screen antialiasing is to simply zoom in. If the scale of of the unwanted white slivers does not magnifiy, then they are probably not actual gaps..
Of course, tiled fills are just as vulnerable to trapping issues as any other artwork. So if your pattern tiles abut completely different colors, the artwork will still need to be trapped as would any other. I only mention it because in a tiled fill, improper trapping (or lack of trapping) can also reveal the tiles' edges in print, even if the file is built correctly.