private void CreatePDF()
        {
            string file,filepatch;
            File plik;
            file = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath;
           // filepatch = System.IO.Path.Combine(file, "test.pdf");
            plik = new File(file, "test.pdf");
            Rectangle rect = new Rectangle(516f, 720f);
            Document document = new Document(rect, 200f, 100f, 100f, 200f);
            try
            {
                OutputStream output = new FileOutputStream(plik);
                PdfWriter pdfwriter = PdfWriter.GetInstance(document, output);

                document.Open();

            }
            catch(FileNotFoundException ee)
            {

            }
        }

PdfWriter pdfwriter = PdfWriter.GetInstance(document, output);