procedure TForm1.Print1Click(Sender: TObject);
// Print preview all layers leaving the original layers unchanged
var
  iImageEnView: TImageEnView;
begin
  iImageEnView := TImageEnView.Create(nil);
  try
    // Transfer the current image, all layers and input/output parameters to destination TImageEnView component
    ImageEnView1.MoveContentTo(iImageEnView);
    iImageEnView.Update;
    // Call LayersMergeAll to merge all layers in one step
    iImageEnView.LayersMergeAll;
    // Show the print preview dialog
    iImageEnView.IO.DoPrintPreviewDialog();
  finally
    iImageEnView.Free;
  end;
end;

Transfers the current image, all layers and input/output parameters to the destination TImageEnView component.

Note:
- This method doesn't copy the images, but transfers pointers to the image buffer
- After the operation the source component will be empty, and all previous images will be removed from "Destination"

  ImageEnView1.Proc.SaveUndo(ieuObjectsAndLayers);
  try
    ImageEnView1.LayersMergeAll;
    ImageEnView1.IO.DoPrintPreviewDialog();
  finally
    ImageEnView1.Proc.Undo;
    ImageEnView1.Proc.ClearUndo; // !!!
  end;

procedure TForm1.PreviewLayers1Click(Sender: TObject);
{ Print Preview Layers. }
var
  iMS: TMemoryStream;
begin
  { Draw the layers to Preview1... }
  ImageEnView1.LayersDrawTo(Preview1.IEBitmap);
  Preview1.Update;
  { Do print preview }
  if Preview1.IO.DoPrintPreviewDialog() then
    begin
      Preview1.Clear;
      { Restore the preview layers }
      iMS := TMemoryStream.Create;
      try
        ImageEnView.LayersSaveToStream(iMS);
        iMS.Position := 0;
        Preview1.LayersLoadFromStream(iMS);
        Preview1.Update;
      finally
        iMS.Free;
      end;
    end;
  end;
end;

procedure TForm1.PrintPreview1Click(Sender: TObject);
{ Print Preview. }
var
  iMS: TMemoryStream;
begin
  { Draw the layers to ImageEnVectPreview1... also draws the objects }
  ImageEnVect1.LayersDrawTo(ImageEnVectPreview1.IEBitmap);
  ImageEnVectPreview1.Update;
  { Do print preview }
  if ImageEnVectPreview1.IO.DoPrintPreviewDialog() then
  begin
     ImageEnVectPreview1.Clear;
    { Update the preview layers and objects }
      iMS := TMemoryStream.Create;
      try
        ImageEnVect1.LayersSaveToStream(iMS);
        iMS.Position := 0;
        ImageEnVectPreview1.LayersLoadFromStream(iMS);
        ImageEnVectPreview1.Update;
      finally
        iMS.Free;
      end;
  end;
end;