Adding text to all page at specific position

So basically I've been trying to add a text vertically at a existing pdf. The existing pdf is in A4 and is first converted to Letter size, then I add a single text per page.

Problem is I think Im having double text per page at different positions instead of only 1 text per page.

using (PdfReader pdfr = new PdfReader(input))
        {
            using (Document doc = new Document(PageSize.LETTER))
            {
                Document.Compress = true;

                PdfWriter writer = PdfWriter.GetInstance(doc, new FileStream(output, FileMode.Create));
                doc.Open();
                PdfPTable table;
                PdfPCell cell;
                Paragraph paragraph;
                PdfContentByte cb = writer.DirectContent;

                PdfImportedPage page;

                for (int i = 1; i < pdfr.NumberOfPages + 1; i++)
                {
                 page = writer.GetImportedPage(pdfr, i);
                  
                 cb.AddTemplate(page, PageSize.LETTER.Width / pdfr.GetPageSize(i).Width, 0, 0, PageSize.LETTER.Height / pdfr.GetPageSize(i).Height, 0, 0);
                 table = new PdfPTable(1);
                 table.TotalWidth = 20;
                 paragraph = new Paragraph("helloworld");
                 cell = new PdfPCell(paragraph);
                 cell.Rotation = 90;
                 cell.BorderWidth = 10;
                 table.AddCell(cell);
                 table.WriteSelectedRows(0, -1, 300f, 200f, writer.DirectContent);
                 doc.Add(table);
                 doc.NewPage();
                }
                doc.Close();
                doc.Dispose();
            }
            pdfr.Dispose();
        }

For some reason another table at the top most is being generated.