open a PDF file in App_Data from link created during Page_Load

Hi,
I know that this topic is not the first on this forum, but I cannot find one post that matches my specific case.

After the user logs in the application retreives the files for that user ID from the ASPNETDB in the App_Data folder. All files are placed as links in 2 tables based on their type (report/quotation). Now when I click a link, I it opens the error page with : Server Error in '/' Application. Illegal characters in path.
The path in the SQL database is "~/files/QuotationNOC091007.pdf" as a Varchar. I user this as the navigateUrl for the link. What did I do wrong?
How can I open the PDF file in Acrobat Reader?
Thanks in advance.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim currentUserName As Object
        Dim currentUserID As Object = Nothing
  &nb ...