Open the TBD.pdf and apply the PdfFileSecurity using the code below. Reviewing the properties after the save, the properties have been changed to mixed characters.
private void setSecurity(string path)
{
var docPrivilege = Aspose.Pdf.Facades.DocumentPrivilege.ForbidAll;
docPrivilege.AllowDegradedPrinting = true;
var fileSecurity = new Aspose.Pdf.Facades.PdfFileSecurity();
fileSecurity.BindPdf(path);
fileSecurity.EncryptFile("test", "test2", docPrivilege, Aspose.Pdf.Facades.KeySize.x128, Aspose.Pdf.Facades.Algorithm.AES);
fileSecurity.Save(path + "cleaned.pdf");
}