SharePoint Workflow or Microsoft Flow?

Hi all,

I'm well experienced in SharePoint, but have never used workflow (don't ask me how).  In my new role we have the following requirement so I was wondering if you have any advice as to whether SharePoint workflow or Microsoft Flow (or a combination / something else) would be best to use.

The requirement is a process flow around the creation, internal approval and signing of contracts for new consultants (or extending contracts for existing consultants):

1. I draft a contract in Word 2016 and store the file in a SharePoint doc library.
2. I currently manually email a link to the contract to others for input / update.
3. I send a link to the contract to either 1 or 2 managers for approval.
   1. They make any changes they see fit and then email me to tell me it's now OK to be sent to the consultant.
   2. In automating the process, we'd need a feedback loop if further changes are required.
4. Once approved, the file needs to be sent to the consultant and 'signed'.  Things to note:
   1. We currently convert it to PDF, storing a copy in the same place as the original Word document, so the consultant can't make changes.
   2. We email the PDF to them as an attachment.
   3. They may want changes made so we'd have to go back through the whole update / manager approval cycle.
   4. At the moment, if they're happy with the contract, they print it out, sign it with a pen, scan it and send it back as an email attachment.
   5. We save the signed copy along with the original Word document and PDF.
   6. The consultant may not yet be on our Office 365 system, but if we could build it to use links (rather than email attachments) and give them access to the specific file(s) they need that would be great.
   7. We use Office 365 Business Premium.

This must be crying-out for some kind of workflow / approval automation, so if I can benefit from the Community's wealth of experience as to where to start that would really help.  It's worth noting that I'm an advanced end user rather than developer so would like to solve this with 'out-of-the-box' functionality.

Hope you can help and thanks as always, Oz