Nothing. I have created a layout, then loaded a map (which has a transparent background). But when i export I get a white background. I want to use the layout though because I have used the reshape tool on the map. Here is a pic
Hi, Lucas. Often it can be more efficient to use, say Adobe Illustrator, to archive the desired layer transparency if you really get stumped in ArcMap. You would use then use the 'stamp tool' or some other method to add the layer after exporting your map. . . Good luck.
I'm having the same issue as Lukas. I tried your method which works for the map frames, but I have a layout with three map frames (Alaska, Hawaii, and other 48 states), and the overall background of the entire layout is still white even though my three map frames have their backgrounds set to transparent.
I have ArcGIS Pro 2.7.2 and I'm still having this issue as well. I set my background (verified both the map frame & the layout) to transparent, and when I exported to PDF it created a white background. I was able to remove the white background when opening the PDF in Adobe Illustrator. However, I will need to repeat this process for a few dozen maps, so that adds a lot more time to the process.