Here's some basic code to do an A4 setup.
Code:
Sub A4Format()
Application.ScreenUpdating = False
With ActiveDocument
With .Range.PageSetup
.BookFoldPrinting = False
.BookFoldRevPrinting = False
.PaperSize = wdPaperA4
.TopMargin = CentimetersToPoints(2.5)
.BottomMargin = CentimetersToPoints(2.5)
.LeftMargin = CentimetersToPoints(2.5)
.RightMargin = CentimetersToPoints(2.5)
.MirrorMargins = False
End With
End With
Application.ScreenUpdating = True
End Sub
Of course, if you have a mix or portrait and landscape Sections and you want different margins for each, you'll need to process them individually.
As for fonts, indents, etc., if the source documents have used Styles consistently, that part of the job is simply a matter of changing the Style definitions; otherwise it's a case of iterating through the paragraphs and updating them individually (perhaps even applying Styles to ensure conformity to corporate standards and simplify future updates).