Add a Formula Field and put it on the detail line.
Bascis Syntax:
WhilePrintingRecords
global RowNumber as Number
RowNumber = RowNumber +1
formula = RowNumber
Format the Detail Section:
The condition for NewPageAfter is
Basic Syntax:
global RowNumber as number
if RowNumber >12 then
RowNumber = 0
formula = true
else
formula = false
end if
Change the 12 to however many rows you want, format the report so each page looks the same.
You can suppress the RowNumber on the detail band if you don't want it to print.
Same type of functionality, with a PageNumber formula and you should be able to figure out how to print only one page if you want.