Created a workflow but need to be able to place the fields (documents from many vendors)

I run numerous documents through a workflow, but the documents themselves are from many vendors and therefore, I need to be able to preview and place fields. It is just slapping a signature block at the end of the document. 

The workflow looks like:

1. Approver 1 (my company)
2. Signor 1 (my company)
3. Approver 2 (me, also sender)
4. Signor 2 (vendor)

Currently, I have to fill in all the steps and specifics as well as custom fields manually. Was hoping the workflow would be a timesaver, but it hasn't worked as planned. Any help figuring this out is appreciated.