This is an entirely different technique, but I felt that is worth posting. Really this question is asking how to print a booklet of Mathematica cells.
Although you can split a page into 2 groups of landscapes cells, IMO the above solution isn't very practical. The above solution doesn't take into account that you might have multiple pages of cells.
The best solution I have found requires that you first run the following code.
changeOptions[nb_] := SetOptions[nb,
StyleDefinitions -> Notebook[{
Cell[StyleData[StyleDefinitions -> "Default.nb"]],
Cell[StyleData[All, "Printout"],
CellMargins -> {{0, 0}, {0, 0}}, ShowCellLabel -> False],
Cell[StyleData["Input", "Printout", StyleDefinitions -> None],
CellMargins -> {{0, 0}, {0, 0}},
LinebreakAdjustments -> {0.85, 2, 10, 1, 1}],
Cell[
StyleData["Input", "PrintoutGray", StyleDefinitions -> None],
CellMargins -> {{0, 0}, {0, 0}},
LinebreakAdjustments -> {0.85, 2, 10, 1, 1}],
Cell[StyleData["Code", "Printout", StyleDefinitions -> None],
CellMargins -> {{0, 0}, {0, 0}}, Background -> GrayLevel[1]],
Cell[StyleData["Text", "Printout", StyleDefinitions -> None],
CellMargins -> {{0, 0}, {0, 0}}, Background -> GrayLevel[1]],
Cell[StyleData["Code", "Printout", StyleDefinitions -> None],
CellMargins -> {{0, 0}, {0, 0}}, Background -> GrayLevel[1]],
Cell[StyleData["Input", "Printout", StyleDefinitions -> None],
CellMargins -> {{0, 0}, {0, 0}},
LinebreakAdjustments -> {0.85, 2, 10, 1, 1}],
Cell[StyleData["Output", "Printout", StyleDefinitions -> None],
CellMargins -> {{0, 0}, {0, 0}}]
}, StyleDefinitions -> "PrivateStylesheetFormatting.nb"],
PrintingOptions -> {
"FirstPageHeader" -> True,
"PrintingMargins" -> {{60, 5}, {10, 10}}
},
PrintingStartingPageNumber -> 1,
PageHeaders -> {
{Cell[TextData[{CounterBox["Page"]}], "PageNumber"], None, None},
{None, None, Cell[TextData[{CounterBox["Page"]}], "PageNumber"]}
},
PageFooters -> {
{None, None, None}, {None, None, None}
}
];
Next export the Notebook as a pdf and open it in Adobe Reader or Foxit Reader. You should then be able to print the cells as a booklet under options. This question discusses possible ways to automate printing out such a booklet.
Alternatively you can use PDF Booklet Creator(fineprint costs $) to create an actual pdf.