add-text-to-pdf.ps1

$dllpath = "B:\tmp\itextsharp.dll"
$inpdf = "B:\tmp\input.pdf"
$outpdf = "B:\tmp\output.pdf"

[void][System.Reflection.Assembly]::LoadFrom($dllpath)
$iText="iTextSharp.text"
$reader = New-Object "$iText.pdf.PdfReader"($inpdf)

$B4 = New-Object iTextSharp.text.Rectangle(1031.91, 728.595)

$doc = New-Object "$iText.Document"($B4)

$BaseFont = [iTextSharp.text.pdf.BaseFont]::CreateFont(
   "C:\windows\fonts\msmincho.ttc,0",
   [iTextSharp.text.pdf.BaseFont]::"IDENTITY_H",
   $True)

$stream = New-Object System.IO.FileStream(
   $outpdf,
   [System.IO.FileMode]::Create)
$writer = [iTextSharp.text.pdf.PdfWriter]::GetInstance($doc, $stream)

$doc.Open()

$page = $writer.GetImportedPage($reader, 1)

$dc = $writer.DirectContent
$dc.AddTemplate($page, 0, -1, 1, 0, 0, 728.595)
$dc.BeginText()
$dc.SetFontAndSize($BaseFont, 20)
$dc.ShowTextAligned(
   [iTextSharp.text.pdf.PdfContentByte]::ALIGN_LEFT,
   "Hello World!",
   45,
   685,
   0)
$dc.EndText()

$doc.Close()
$stream.Close()
$reader.Close()