使用Powershell和iTextSharp实现水印

Add-Type -Path "C:\path\to\itextsharp.dll"

$pdfPath = "C:\path\to\input.pdf"
$pdfReader = New-Object iTextSharp.text.pdf.PdfReader($pdfPath)

$outputPath = "C:\path\to\output.pdf"
$pdfStamper = New-Object iTextSharp.text.pdf.PdfStamper($pdfReader, [System.IO.File]::Create($outputPath))

$font = [iTextSharp.text.BaseFont]::CreateFont([iTextSharp.text.BaseFont]::HELVETICA, [iTextSharp.text.BaseFont]::CP1252, [iTextSharp.text.BaseFont]::EMBEDDED)
$color = [iTextSharp.text.BaseColor]::GRAY
$opacity = 0.5
$text = "Confidential"

for ($i = 1; $i -le $pdfReader.NumberOfPages; $i++) {
    $pdfContentByte = $pdfStamper.GetOverContent($i)
    $pdfContentByte.BeginText()
    $pdfContentByte.SetFontAndSize($font, 48)
    $pdfContentByte.SetColorFill($color)
    $pdfContentByte.SetGState((New-Object iTextSharp.text.pdf.PdfGState($opacity)))
    $pdfContentByte.ShowTextAligned([iTextSharp.text.Element]::ALIGN_CENTER, $text, 300, 400, 45)
    $pdfContentByte.EndText()
}

$pdfStamper.Close()
$pdfReader.Close()