If I understand this correctly, you just need to change your fields so that the table starts after the header.
From http://www.docjar.org/docs/api/com/lowagie/text/Document.html
public Document(Rectangle pageSize, float marginLeft, float marginRight, float marginTop, float marginBottom)
For instance:
final Document document = new Document(PageSize.A4, 50, 50, 165, 50);
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