Sharing Folders with Samba seems like an impossible task...

I have a unbuntu 16.04 server, a MacBook, and a printer. The goal is to create a folder on the server that the printer can write to and the user(s) can access.

I’ve created a user called printer on the server.
I’ve created a folder called documents on the server.
I’ve created a Samba Share called masterdocuments with the printer -and- me as a valid user.

When I try to mount the share on my Mac, I am only able to do so when I use the credentials of the printer user. How do I:

a) give my printer read/write access to that folder and
b) give myself read/write access to that same folder?

I’ve been trying various settings for over 2 hours and I’m stuck.