Here is a snippet of my code
Dim table As iText.Layout.Element.Table = New iText.Layout.Element.Table(4)
table.SetWidth(pagesize.GetWidth - 40)
Dim something
Dim result As LayoutResult = table.CreateRendererSubTree().SetParent(doc.GetRenderer()).Layout(New LayoutContext(New LayoutArea(1, New Rectangle(0, 0, 400, 10000.0F))))
tableHeight = result.GetOccupiedArea().GetBBox().GetHeight()
This is how I was able to find the table height in itext7, hopefully it can help someone.