// Reduce the size of the PDF file by lowering the quality of the images and enabling JPEG compression (B is a TIEBitmap)
ImageEnView1.IOParams.PDF_Compression := ioPDF_JPEG;
ImageEnView1.IOParams.JPEG_Quality    := 75;
for i := 0 to ImageEnView1.PdfViewer.Objects.Count - 1 do
begin
  oPDF := ImageEnView1.PdfViewer.Objects[i];
  if (oPDF.ObjectType = ptImage) then
  begin
    B := TIEBitmap.Create();
    try
      if oPDF.GetImage( B ) then
      begin
        B.Resample( 0.5 );
        oPDF.SetImage(B);
       end;
    finally
      B.Free;
    end;
  end;
end;
ImageEnView1.PdfViewer.ReloadPage();