merged PDFs are showing as "in use" by WebKit when I try to delete them

Question

I am merging multiple PDFs into one PDF using Node, iTextSharp, and Edge. Everything is working until I try to delete the original PDFs. They are "in use" by WebKit. If I close NW they are released of course. I can run the same code but using a console app and the files can be deleted immediately. Any ideas?

---NW javascript--- 
var edge = require('edge');
var dotNetFunction  = edge.func({
   assemblyFile: 'E:/VisualStudio2013Projects/Edge/Edge.PDF/bin/Debug/Edge.PDF.dll',
   typeName: 'Edge.PDF.StartUp',
   methodName: 'MergePDF'
});
var payload = {
   targetPDF: 'C:/test/042715JM75-NEW.pdf',
   filesPDF: ['C:/test/042715JM75.pdf','C:/test/042715JM75-sales-copy.pdf'],
};
---C#---
namespace Edge.PDF
{
 public class StartUp
  {
   public async Task<object> MergePDF(dynamic input)
   {
    return await Task.Run(async () =>
    {
       string lJsonData = string.Empty;
       string targetPDF = input.targetPDF;
       var filesPDF = input.filesPDF;
       using (FileStream stream = new FileStream(targetPDF, FileMode.Create))
            {
                Document pdfDoc = new Document(PageSize.A4);
                PdfCopy pdf = new PdfCopy(pdfDoc, stream);
                pdfDoc.Open();

                var files = filesPDF;                   
                foreach (string file in files)
                {               
                    pdf.AddDocument(new PdfReader(file));
                }
                if (pdfDoc != null)
                    pdfDoc.Close();
            }
            return Newtonsoft.Json.JsonConvert.SerializeObject(new { success = true});
                });
    }
}
}

Answer 1

Instead of creating an array of files (filesPDF), you should create an array of PdfReader instances. Add each of these readers to the pdf and after closing the pdf, loop over the readers once more to close them:

foreach (PdfReader reader in fileReaders) {               
    reader.Close();
}

Now the filehandlers will be released, and you'll be able to delete the files.