I specified a location on my network here. If you haven't modified the script to use a new location on your own drive, or network drive, then you will get that error.
In the code I uploaded last, it was written like this:
"/Volumes/network save location"
That needs to be where you want the file saved. It happens three times, once each for 300 DPI, 150 DPI and 72 DPI, so be sure to change it that many times.