How can i save my populated PDF instead of saving to hardcoded file?

I have successfully implemented the iTextSharp.text.pdf to populate a PDF template file we have setup. Currently that file is being save automatically to a specific folder on local machine...but we don't want that, we want the populated PDF to be saved by the user to the folder of their choice on their pc. We do not want to keep any of these files on the server once this application gets published.
the below code creates the hardcoded file path and it is populated, but the portion at the bottom that prompts the user to save the file, creates a pdf with the file name format we want, but the file is always 20k and wont open. How can I change the below code to not actually create the file on the server, but to create it to the users pc when they chose to save it?

How can i change this to send the outputfile to the user instead of saving to the server.
using (FileStream outfile = new FileStream(outputfile, FileMode.Create)) ...