Multiple documents may be added in several ways –
1. Zip up the files together and add the single Zip file to the Upload Area.
or
2. Click in the Upload Area, navigate to the folder containing your files and select individual files by continuously holding the CTRL key and clicking the mouse on each file to be added (works easiest if you have already located the upload files together in the one folder).
or
3. Drag and Drop your files into the Upload Area. As in option two, open the folder containing your files then select individual files by continuously holding the CTRL key and clicking the mouse on each file to be added. Next Drag and Drop them together onto the Upload Area (works easiest if you have already located the upload files together in the one folder).
NOTE: Attempting to add multiple files individually, one after the other, to the Upload area will NOT work for option 2 and 3.