如何使用asp.net中的itextsharp将多个pdf文件合并为单个文件

Question

我在结合多个pdf后使用以下代码生成一个pdf，但它始终会生成没有页面的黑色pdf文件。

List<PdfReader> readerList = new List<PdfReader>();
foreach (string filePath in filesPath)
{
    PdfReader pdfReader = new PdfReader(filePath);
    readerList.Add(pdfReader);
}

//Define a new output document and its size, type
Document document = new Document(PageSize.A4, 0, 0, 0, 0);
//Create blank output pdf file and get the stream to write on it.
PdfWriter writer = PdfWriter.GetInstance(document, new FileStream(outPutFilePath, FileMode.Create));
document.Open();

foreach (PdfReader reader in readerList)
{
    for (int i = 1; i <= reader.NumberOfPages; i++)
    {
        PdfImportedPage page = writer.GetImportedPage(reader, i);
        document.Add(iTextSharp.text.Image.GetInstance(page));
    }
}
document.Close();
Response.AppendHeader("content-disposition", "inline; filename=OutPut.pdf");
Response.ContentType = "application/pdf";