When loading a document, the Editor will optimize the document like replacing a sequence of colored boxes by a smooth shading (which is more suitable for scaling to larger sizes) and like converting text into editable text.
This might go wrong in very rare cases (accidently replace a sequence of boxes into a gradient).
Using this “EPS/PDF Compatibility mode ” option will disable IGOR (Intelligent Graphic Object Recognition) and load the file as it is originally.