PDFsharp Merge PDF in Memory

using PdfSharp.Pdf;
using PdfSharp.Pdf.IO;
using System.Collections.Generic;
using System.IO;

public static byte[] Merge(List<byte[]> files)
{
    var streams = new List<Stream>();

    //add the byte arrays to the stream list
    foreach (var file in files)
    {
        streams.Add(new MemoryStream(file));
    }

    return Merge(streams);
}


public static byte[] Merge(List<Stream> files)
{
    using (var merged_pdf = new PdfDocument())
    {
        //loop all the uploaded files
        foreach (var file in files)
        {
            //read the pdf file from the stream
            var source_pdf = PdfReader.Open(file, PdfDocumentOpenMode.Import);

            //loop each page in the source and add them to the new pdf
            for (int i = 0; i < source_pdf.PageCount; i++)
            {
                merged_pdf.AddPage(source_pdf.Pages[i]);
            }
        }

        //copy the new pdf to a memorystream
        byte[] bin = null;
        using (var stream = new MemoryStream())
        {
            merged_pdf.Save(stream, false);
            bin = stream.ToArray();
        }

        //return the merged pdf as byte array
        return bin;
    }
}