how to give pdfcoument a name in c#

//Create a new PDF document.
PdfDocument document = new PdfDocument();
//Add a page to the document.
PdfPage page = document.Pages.Add();
//Create PDF graphics for the page.
PdfGraphics graphics = page.Graphics;
//Set the standard font.
PdfFont font = new PdfStandardFont(PdfFontFamily.Helvetica, 20);
//Draw the text.
graphics.DrawString("Hello World!!!", font, PdfBrushes.Black, new Syncfusion.Drawing.PointF(0, 0));
//Save the PDF document to stream
MemoryStream stream = new MemoryStream();
document.Save(stream);
//If the position is not set to '0' then the PDF will be empty.
stream.Position = 0;
//Close the document.
document.Close(true);
//Defining the ContentType for pdf file
string contentType = "application/pdf";
//Define the file name
string fileName = "Output.pdf";
//Creates a FileContentResult object by using the file contents, content type, and file name
return File(stream, contentType, fileName);