Provided that you Know the name and location of the file on the server, how is it possible to prompt the user to save said file on their desktop, whether it be to their downloads folder or elsewhere?

My scenario is a PDF file is generated on the server (C#). The file is saved to a folder there on the server. But the user needs to be able to save that file to their desktop.

Is this possible? If so, what event can I use for this? The user will click a "Generate PDF" button on the web page/form, and after the PDF is generated and saved there, I want to prompt the user to save the file locally.