How are you populating this file with information?
Let's pretend you have all of your information in a variable called '$data'. You could link the "Save File" to a PHP script with the contents like so:
header ("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header ("Content-Type: application/octet-stream");
header ("Content-Length: " . strlen($data));
header ("Content-Disposition: attachment; filename=\"info.txt\"");
echo $data;
Sorry for the weird spacing - I copied and pasted the headers from a downloads script I made.