Who can see a RFP (Request for Proposal)?

The only people who can see a RFP are users within your company and the vendors who are invited to bid on that particular project. If you have invited a collaborator from another company to the project team (if you are a producer at an ad agency and invite someone from the brand or purchasing team at your client company to the project team, for example), the collaborator(s) will see the RFP as well.