Was wondering if there is some "easy" way of display whether a document is approved, pending, or still in development, in its properties and/or the document library?
You need to do little bit of development for that. Create one custom aspect with one property like wfstatus. Create one rule which add that aspect with property value appropriately.
var props = new Array(1); props["custom:wfstatus"] = "approved"; document.addAspect("custom:wfinfoaspect", props);