TOPIC:

doc.MovePage(1, 0);
doc.Save();
doc.Close();
stream.Dispose();
stream = await file.OpenAsync(FileAccessMode.ReadWrite);
using (var inputStream = stream.GetInputStreamAt(0))
{
          using (var dataReader = new Windows.Storage.Streams.DataReader(inputStream))
          {
               uint bytesAvailable = await dataReader.LoadAsync((uint)stream.Size);
                byte[] byArray = new byte[bytesAvailable];
                dataReader.ReadBytes(byArray);
                Windows.Storage.StorageFolder storageFolder =
                           Windows.Storage.ApplicationData.Current.LocalFolder;
                Windows.Storage.StorageFile sampleFile =
                            await storageFolder.CreateFileAsync("sample.pdf", Windows.Storage.CreationCollisionOption.ReplaceExisting);
                var destStream = await sampleFile.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite);
                 using (var outputStream = destStream.GetOutputStreamAt(0))
                 {
                        using (var dataWriter = new Windows.Storage.Streams.DataWriter(outputStream))
                        {
                               dataWriter.WriteBytes(byArray);
                               await dataWriter.StoreAsync();
                                await outputStream.FlushAsync();
                          }                                    
                 }
                 destStream.Dispose();
          }
          stream.Dispose();
 }