The Digital Downloads Importer Plugin allows you to easily bulk import .pdf, .zip, .odt and any other file type, excepting jpgs*.
If you're tired of uploading digital products one at a time, Digital Downloads Bulk File Importer for WordPress is exactly what you're looking for. Use the streamlined interface to make setting up your store painless. For more information read the readme
Bulk import .pdf, .zip, .odt and any other digital file types. Makes setting up stores lightning fast.