I’m afraid this is not possible directly, but there may be a workaround. However, one element is missing in my suggestion.
Provided there is a built-in variable to capture the present page number (I only found variable PAGE containing total page count), you can insert a custom field associated with a formula.
- In the footer area (meaning you enabled it in the page style or
Format>Page), Insert>Fields>Other
- Go to
Variables tab and select Insert Formula
- In the Formula text box, type (
pagenr + 1) DIV 2 which compute the sheet number (in duplex printing)
- Click
Insert, then Close
BIS CAVEAT: in the formula above, I wrote pagenr for the running page number but I did not find the real variable name in the built-in help, if it ever exists. I need help from a developer to clear the point. Variable PAGE is the total page count which does meet the requirement.