Downloadable document approval, with yes no loop without requirement for extra licences

Hello

 I wonder if anyone can help a new system admin - I want to set up a document approval loop where a 3rd party

1. is notified to upload a document to me

2. I can download that document, and analyse it outside of workfront  (I need to look at dimensions and format of the file, expecting .ai)
3. I can say yes approved or no Please upload a revised version of that file

repeat until approved.  The issue is I will be sending this request to 100's of individuals over a long period of time and I cannot afford a licence for each individual recipient.

Any assitance gratefully received :0)