wpf - iTextSharp 在 WPF 中生成损坏的 PDF

Question

我是使用 iTextSharp 编程的新手。我有一个在 PDF 文件中写入的应用程序。文件是用word写的，然后保存在PDF中（有2页）。我的问题是，当我想在 PDF 上书写时，我看到了已写入的数据，但输出的 PDF 已损坏。我不明白为什么 PDF 会损坏？

    Public Sub WriteForm(TemplateFilePath As String, NewFilePath As String, data As FormData)
    'input output files
    Dim oldFile As String = TemplateFilePath
    Dim newFile As String = NewFilePath

    'if file already exists then delete it
    If System.IO.File.Exists(newFile) Then
        System.IO.File.Delete(newFile)
    End If

    ' open the reader
    Dim reader As New PdfReader(oldFile)
    Dim size As Rectangle = reader.GetPageSizeWithRotation(1)
    Dim document As New Document(size)

    ' open the writer
    Dim fs As New FileStream(newFile, FileMode.Create, FileAccess.Write)
    Dim writer As PdfWriter = PdfWriter.GetInstance(document, fs)
    document.Open()

    'write data to first page
    Me.WriteData(reader, writer, data)

    'write second page
    Me.AppendCopiedPage(document, writer, reader, 2)

    ' close the streams 
    document.Close()
    fs.Close()
    writer.Close()
    reader.Close()

End Sub

'写数据的代码

    Private Sub WriteData(reader As PdfReader, writer As PdfWriter, data As FormData)`
    Dim cb As PdfContentByte = writer.DirectContent
    Dim bf As BaseFont = BaseFont.CreateFont(BaseFont.TIMES_ROMAN, BaseFont.CP1250, BaseFont.EMBEDDED)
    cb.SetColorFill(BaseColor.BLACK)
    cb.SetFontAndSize(bf, 10)

    ' create the first page and add it to the pdf
    Dim page1 As PdfImportedPage = writer.GetImportedPage(reader, 1)
    cb.AddTemplate(page1, 0, 0)
    Me.WriteText(cb, data.SID, 110, 653)
           ...
End Sub