That setting is inherited from the table style so it could be as simple as changing the table style setting if your document is extraordinarily well formatted. However, typically tables have a large number of local formatting applied to them so the style setting is likely to be overridden in various locations so a more direct method will need to be used.
You can apply the AllowBreakAcrossPages setting without having to go to every single row and cell in the table. This avoids the need to worry about tables with merged cells
Code:
Sub TablePageBreaker()
Dim aTbl As Table
For Each aTbl In ActiveDocument.Tables
aTbl.Rows.AllowBreakAcrossPages = False
Next aTbl
End Sub