Hi Shaon,
Thanks for replying.
I understand that the problem is so to speak with safari and not the wpdm plugin.
My point was that just like google uses application/octet-stream to force Safari to download the file as is without adding the .txt suffix so could your plugin.
This would be a big improvement to the plugin. If you examine the code behind this link https://docs.google.com/file/d/0B-FdGXllwjR1U1hTeEtINVg0YTA by clicking the link and then typeing ctrl U (windows) or command U (mac) then you could see how to do it.
It would be great to see if you good do this, keep up the good work,
Trevor