How to change the default printing options using commmand?

Question

I am looking for something like this:

SetOptions[EvaluationNotebook[], "PaperSize" -> "A3"]

The options are listed, but where do I find the arguments? Say for A3 paper, do I use A3 or "A3" or "a3paper"?

and it looks like it takes two inputs? How?

I can change them everytime from the drop down menu, but it's not very efficient.

Answer 1

According to this A3 is {842, 1190} printers points, so to set that and a variety of print related options programmatically:

SetOptions[EvaluationNotebook[],
 RulerUnits -> "Points",
  PageHeaders -> {{
        Cell[
          TextData[{
              CounterBox["Page"]}], "PageNumber"], 
        Cell[
          TextData[{"Author"}], "Header"], None}, {None, 
        Cell[
          TextData["Article title"], "Header"], 
        Cell[
          TextData[{
              CounterBox["Page"]}], "PageNumber"]}},
  PageFooters -> {{None, None, None}, {None, None, None}},
  PageHeaderLines -> {False, False},
  PrintingOptions -> {"FacingPages" -> True,
    "FirstPageFace" -> Right,
    "FirstPageFooter" -> True,
    "FirstPageHeader" -> False,
    "Magnification" -> 1,
    "PageFooterMargins" -> {30, 30},
    "PageHeaderMargins" -> {60, 60},
    "PageSize" -> {842, 1190},
    "PaperSize" -> {842, 1190},
    "PrintCellBrackets" -> False,
    "PrintRegistrationMarks" -> False,
    "PrintingMargins" -> {{90, 90}, {60, 90}}}
 ]

Answer 2

This should get you started for A3:

SetOptions[EvaluationNotebook[], 
 PrintingOptions -> {"PaperSize" -> 
  Round[72*
   QuantityMagnitude@
    UnitConvert[Quantity[#, "Millimeters"] & /@ {2*210, 297}, 
     "Inches"]]}]

Background

Mathematica assumes 72pt per inch for the PaperSize-option. The example above just uses the Quantity functionality for conversion from the DIN-dimensions (I used the equivalent of two A4 sheets for reference).

Be aware, though, that the PrintingOptions feature might change in the future (see the online reference for that warning).