[eluser]Jaketoolson[/eluser]
Did you load the 'download' helper file?
Code:
$this->load->helper('download');
Also, are you generating the pdf first then downloading it? One way to narrow down your problem is to upload an already created PDF file to the server and point to it correctly in your get_pdf() function. If this works correctly, then its a problem with your PDF creation method/function.