Easy to achieve if you are just going every x words. A bit more complex if you want to find x words then adjust forward or back to a paragraph mark.
Code:
Sub Macro1()
Dim x As Long, lStep As Long
lStep = 50 'how many words before a page break
If ActiveDocument.Words.Count > lStep Then
For x = lStep To ActiveDocument.Words.Count Step lStep
ActiveDocument.Range.Words(x).InsertAfter Chr(12)
Next x
End If
End Sub