Is there any way to create a double outlined shape (triangle) for example ?
(i've noticed i can create another similar shape in the back but i'm looking for more elegant solution)
For Visio 2010 and early the quick summary is that you have to create a custom Line Pattern. The full steps and a screencast are here: http://viziblr.com/news/2011/10/4/visio-ndash-creating-double-lined-shapes.html
For Visio 2013, Visio has a built-in feature for double-lined borders.