How to reduce gradient banding in InDesign CS6?

I designed a vinyl fabric banner (10 ft x 2 ft) for a customer. It has a 4 colour logo on it plus a gradient tint in the background across the 10 ft length. The art was created in InDesign CS6 and exported as a high res PDF (3.4 mb). The printer called to say the gradient had visible steps/banding. I did not notice it on my screen until I zoomed in 100% size. He ended up using a TIFF file (6.5 mb) that I sent him where the banding is barely noticeable.



I have two similar banners to prepare in InDesign. Any ideas how to remove the banding effect and have a seamless gradient?



iMac 24", Mac OSX10.6.8, InDesign CS6

via ehMac.ca http://www.ehmac.ca/showthread.php?t=114737&goto=newpost