Polygon Pours and Board Outlines

You can easily pull in polygon pours from the board edges by copying the Board Outline to the Keep-Out Layer. 

As shown below I have copied the Board Outline to the Keep-Out Layer and changed the line width to 1mm (~40mils). This will pull the polygon pours in from the board edges by 1/2 of the keepout line width 0.5mm (~20mils) plus any applicable design rules.