Try this code
Step 1:
<asp:LinkButton ID="LinkButton2" runat="server" onclick="LinkButton2_Click">Download PDF</asp:LinkButton>
Step 2: Create folder and place exe in that folder.........
Step 3:
protected void LinkButton2_Click(object sender, EventArgs e)
{
string path = Server.MapPath("AdbeRdr910_en_US.exe");
string name = Path.GetFileName(path);
string ext = Path.GetExtension(path);
string type = "";
if (ext != null)
{
switch (ext.ToLower())
{
case ".htm":
case ".html":
type = "text/HTML";
break;
case ".txt":
type = "text/plain";
break;
case ".GIF":
type = "image/GIF";
break;
case ".pdf":
type = "Application/pdf";
break;
case ".exe":
type = "Application/exe";
break;
case ".doc":
case ".rtf":
type = "Application/msword";
break;
}
}
Response.AppendHeader("content-disposition", "attachment; filename=" + name);
if (type != "")
Response.ContentType = type;
Response.WriteFile(path);
Response.End();
}