/**
  * Sets the number of scene units visible per page.
  *
  * @param perPage the number of scene units visible per page.
  */
 public void setPerPage(final double perPage) {
   this.perPage = perPage;
   double content = paper.getPrintableHeight();
   if (renderHeader) {
     content -= scene.getHeaderSize().getHeight();
   }
   if (renderFooter) {
     content -= scene.getFooterSize().getHeight();
   }
   scene.setScalingFactor(content / perPage);
 }
 public void setScalingFactor(final double scale) {
   scene.setScalingFactor(scale);
 }