I found this on the Actuate Club Forum. Looks complicated, have fun
How to reset page numbers at the group level for Actuate Reports:
1. Add two integer controls to the PageStyle of your report. The ValueExp will be tempCounter + 1 and tempCounter resepectively
2. Double click on the New Report App and select Variables tab Add a new variable called tempCounter (Integer, Static, and Public)
3. To the first group section, modify the sub Start method as follows:
Sub Start( )
Super::Start( )
tempCounter=0
End Sub
4. If not already present, add a second Content Group section to your existing group section.
5. Override the Sub Finish method as follows:
Sub Finish( )
Dim PageIterator As AcIterator
Dim Pg As NewReportApp:

age //Page = your Pagestyle component name
Dim PgList As NewReportApp:

ortrait //Portrait = Pagelist component name
Dim currControl As AcIntegerControl
Dim count As Integer
Dim currIndex As Integer
Set PgList=GetPageList()
currIndex=PgList.GetPageCount()
Set PageIterator=PgList.GetContentIterator
PageIterator.SkipTo(currIndex-tempCounter+1)
Do While PageIterator.HasMore()
Set Pg=PageIterator.GetNext()
Set currControl=Pg.FindContentByClass("NewReportApp:

age::IntegerControl2") //name of second integer control
currControl.DataValue=tempCounter
Loop
Super::Finish( )
End Sub
6. Override the Sub StartPage( page As AcPage ) as follows:
Sub StartPage( page As AcPage )
tempCounter = tempCounter+1
Super::StartPage( page )
' Insert your code here
End Sub