VersionedDocument.cs

public class VersionedDocument {

  // member fields
  private TextControl _textControl;
  private string _filename;

  // properties
  public List<EmbeddedFile> Attachments { get; set; } = new List<EmbeddedFile>();

  // constructor
  // attach a TextControl and set filename
  public VersionedDocument(TextControl textControl, string filename) {
    _textControl = textControl;
    _filename = filename;
  }

  // saves the current version as the visible representation
  // and attaches the current version to the attachments
  public void SaveDocument() {
    // save current document from connected TextControl
    byte[] baCurrentDocument;
    _textControl.Save(out baCurrentDocument, BinaryStreamType.InternalUnicodeFormat);

    // create a unique filename
    var uniqueFilename = Guid.NewGuid().ToString() + ".tx";

    // add the latest attachment
    Attachments.Add(new EmbeddedFile(uniqueFilename, baCurrentDocument, null));

    // use a temporary ServerTextControl to save the document
    using (ServerTextControl tx = new TXTextControl.ServerTextControl()) {
      tx.Create();
      tx.Load(baCurrentDocument, BinaryStreamType.InternalUnicodeFormat);

      // set the embedded files using the SaveSettings
      SaveSettings saveSettings = new SaveSettings() {
        EmbeddedFiles = Attachments.ToArray()
      };

      // save the file
      tx.Save(_filename, StreamType.AdobePDF, saveSettings);
    }
  }

  public void LoadDocument(string filename) {
    // temporary ServerTextControl to handle attachments
    using (ServerTextControl tx = new ServerTextControl()) { 
      tx.Create();

      LoadSettings ls = new LoadSettings() {
        PDFImportSettings = PDFImportSettings.LoadEmbeddedFiles
      };

      // load the PDF document
      try {
        tx.Load(filename, StreamType.AdobePDF, ls);
      }
      catch { throw; }

      // store attachments
      Attachments = ls.EmbeddedFiles?.ToList();

      // get latest attachment
      var latestAttachment = Attachments.OrderByDescending(c => c.CreationDate).First();

      // load attachment into connected TextControl
      try {
        _textControl.Load(
          (byte[])latestAttachment.Data,
          BinaryStreamType.InternalUnicodeFormat);
      }
      catch { throw; }

      // set the current filename
      _filename = filename;
    }
  }
}