arcgis-desktopcartographylayoutstransparency
Is there a way to create a transparent box in the ArcGIS layout view similar to the one in the screenshot? I have tried without success adding a transparent box by inserting a neatline, adding a new dataframe and adding a polygon with the draw tools. The only way I can envision doing this is by adding a shapefile to the layout and specifying transparency, although this approach seems awfully convoluted.
Unless you want to try to implement an ArcObjects solution for this, as suggested by @blah238, your best bet appears to be to submit a new ArcGIS Idea for it.
I would target that enhancement request for ArcGIS Pro rather than ArcMap. However, there is not yet an ArcGIS Pro category available for you to do that.
Try using an annotation feature class for the 'DRAFT' text, manually editing the text, and setting the transparency for the layer at 50%.
This allows you to see the features under the text, and it is not necessary to export the document for use in another program.
Best Answer
The approach you you mention does sounds unorthodox, it is, however, the only way you can do it in ArcGIS. It is actually more efficient doing this inside ArcMap as you suggest as oppose to a 3rd party image editing software outside of ArcMap. The benefit is that you don't have to post-process your cartography in a another application and it is therefore far easier to update your map down the road if need be. Personally, I do everything I can in ArcMap. Until recently I even drew my logos and complex north arrows in ArcMap and exported to EMF so that I can get the transparent background - as of 10.2 this is no longer necessary - ArcMap now honors transparency of EMF files created in other applications.
Your approach works for me and even though I am fluent in Photoshop and Illustrator It is still simpler to do cartographic effects such as the one you mention in ArcMap. (I have a "Document Data" FGDB container stored in the same directory where my Map Document is in which i keep various odds and ends above and beyond the primary map datasets; cartographic buffer rings, local annotations, and transparent boxes!)
When producing a cartographic "marvel" destined for the printing presses,the final product matters and if I can do it in ArcMap without having to go to Illustrator I will.
In fact, looking at your example, I would recommend to even create the overview map inset in ArcMap; just add a separate data frame. So long you only use vector data, the backround will be transparent. If You want to include a raster such as hillshade in the inset, you can still build the inset with a transparent background in ArcMap - export to EMF - add image to map