I have been testing a new internal web portal which will give employees access to a large database of PDF documents. This portral appears to deliver all PDFs with a generic filename "FILE0" and with no extension. When we access the portal with Internet Explorer 8 and Adobe Reader X(10), the user is able to view the PDF. The same browser with Adobe Reader 8 or 9 is not able to view the PDF. Can anyone shed light on how this works? How does Adobe Reader X know that these extensionless files are PDFs? Can previous version of Reader be made to do this?