Can I use Automated Workflow Integrator to pull down files that have been uploaded to the Pressero storefront using a form?

Unfortunately, Automated Workflow Integrator can only interact with orders that are placed within Pressero.
If a file is uploaded via a form, this is not typically done as part of an order as there is no option to include a file upload option via the form at a product level. 
If a person is completing a form on a custom page, they do have the option to upload a file; however this file is not part of an order and the link to the file is typically only sent within the "Form Submitted" email.  You may also access the uploaded file via Tools > File manager.  
The file included in the email or in File Manager would not be available for Automated Workflow Integrator because it would not be part of an order that has been placed.