[(Slurp) Stealing all files with specified extensions, regardless of hard-drive?]

Are you sure you didn't reply to the wrong thread, kdodge?

[(Slurp) Stealing all files with specified extensions, regardless of hard-drive?]

In Hak5's blog post about stealing files with the USB Rubber Ducky, they only targeted the documents folder on the C: drive. I'm looking to steal all .PDFs/Excel spreadsheet, regardless of their directory/drive. Can anyone show me how this is done? I have been trying all day now, but can't get a satisfactory result. 

Thanks in advance! Any help would be greatly appreciated.