c# - iTextSharp - footer on top of the PDF page issue -

i working on older project itextsharp version 3.1.7.0. header part working fine, have issues footer. when add text, footer showing should - @ bottom of page. when add table instead of text, footer jumps on top of page. code, missing?

document document = new document(pagesize.a4, 36, 40, 0, 30);  pdfptable table = new pdfptable(3); pdfpcell cell = new pdfpcell(new phrase("table header")); cell.colspan = 3; cell.horizontalalignment = 2;  table.addcell(cell); table.addcell("cell1example"); table.addcell("cell2example"); table.addcell("cell3example"); table.addcell("cell4example"); table.addcell("cell5example"); table.addcell("cell6example");  phrase footerphrase = new phrase(); footerphrase.add(table); footerphrase.leading = 10;  headerfooter footer = new headerfooter(footerphrase, false); document.footer = footer;