使用SaveToStream将Excel转换为PDF(只读/不可编辑版本)

我正在使用Spire XLS库将excel转换为pdf。有没有办法将只读/不可编辑的属性添加到 pdf 文件中？

我的编码如下。谢谢。

Workbook wb = new Workbook();
Worksheet ws = wb.Worksheets[0];
//set cell value
using (MemoryStream memoryStream = new MemoryStream())
{
   wb.SaveToStream(memoryStream, Spire.Xls.FileFormat.PDF);
   byte[] bytes = memoryStream.ToArray();
   memoryStream.Close();
   using (MailMessage mailMessage = new MailMessage())
   {
       // SMTP Setting
       mailMessage.Attachments.Add(new Attachment(new MemoryStream(bytes), "Attachment.pdf", "Application/pdf"));
   }
}