Hey there! I totally get the frustration—you’ve nailed merging two PDFs but hit a wall when trying to turn that iTextSharp.text.Document into a byte array. Let’s sort this out quickly.

The Core Issue #

The Document object in iTextSharp is just an abstraction for building your PDF content—it doesn’t actually store the raw byte data itself. To get a byte array, you need to route the Document’s output to a MemoryStream first, then extract the bytes from that stream.

Step-by-Step Solution #

Here’s how to adjust your code to capture the merged PDF as a byte array:

• Use a MemoryStream as the output target for your PdfWriter
• Execute your merge logic as you did before
• Properly close the Document and Writer to ensure all data is flushed to the stream
• Extract the byte array from the MemoryStream

Working Code Example #

using System.IO;
using iTextSharp.text;
using iTextSharp.text.pdf;

public byte[] MergePdfsToByteArray(string pdfPath1, string pdfPath2)
{
    using (var outputStream = new MemoryStream())
    {
        // Initialize Document and bind it to the MemoryStream via PdfWriter
        var document = new Document();
        var writer = PdfWriter.GetInstance(document, outputStream);

        document.Open();

        // Add pages from first PDF
        using (var reader1 = new PdfReader(pdfPath1))
        {
            for (int pageNum = 1; pageNum <= reader1.NumberOfPages; pageNum++)
            {
                PdfImportedPage importedPage = writer.GetImportedPage(reader1, pageNum);
                document.Add(Image.GetInstance(importedPage));
            }
        }

        // Add pages from second PDF
        using (var reader2 = new PdfReader(pdfPath2))
        {
            for (int pageNum = 1; pageNum <= reader2.NumberOfPages; pageNum++)
            {
                PdfImportedPage importedPage = writer.GetImportedPage(reader2, pageNum);
                document.Add(Image.GetInstance(importedPage));
            }
        }

        // Critical: Close the document and writer to flush all content to the stream
        document.Close();
        writer.Close();

        // Convert the stream to a byte array
        return outputStream.ToArray();
    }
}

Key Notes #

• Always close the Document and Writer: If you skip this, the MemoryStream might be missing the final parts of the PDF (like the cross-reference table), leading to corrupted data.
• Use using blocks: This ensures resources like PdfReader are properly disposed, preventing memory leaks.
• Avoid accessing the stream before closing the Document: The Document holds some data in memory until it’s closed, so the stream won’t have the full PDF until then.

Give this a try—your merged PDF should now convert to a byte array without issues!

内容的提问来源于stack exchange，提问作者paras