I'm working on a poster that has one data frame in the background to provide some subtle background colors and other data frames on top. In the data frame properties for all the data frames on top, I've set the background to "none". Looking at it on my screen, this has the effect of seeing the background colors behind the data frames on top, which is what I want. However when I print (or convert to PDF), any data frame that contains a raster prints with a white box in the background (which covers the background color). Data frames containing only vector data work fine.
For the purposes of this poster I could theoretically convert all the raster data to vector as a workaround but I'm wondering if anyone has a better solution.
Unfortunately I didn't find a solution and I called Esri tech support and they couldn't give me a solution either. So my workaround was to convert the raster data to vector. Kind of a pain but in my case there were only about 3 or 4 raster layers that needed to be converted so it didn't end up taking too long.