No Replace Button Found

I wanted to update the files at http://dannyman.toldme.com/2011/08/10/san-jose-tube-map/ so I installed this plugin. I don’t see any replacement function under “Edit Image.” Also, I can not “edit Image” on the PDF. A button within the “Show Image” screen would be most useful. This sort of basic functionality really should be core!

Thanks, anyway.

-danny