Virtual path and physical path

Instead of saving app in c:\inetpub\wwwroot, I save myOrder app into D:\myWeb\myOrder. To open it, user can type http://localhost/myOrder/Default.aspx

There is a aspx file located in D:\oldorder\oldorder.pdf

There is a button in default.aspx page (D:\myWeb\myOrder\default.aspx).

How to use response.redirect to open oldorder.pdf file from http://localhost/myOrder/Default.aspx ?

(pdf viewer was intalled)
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