The EPDM client is just one program, and you select the install type and the license type.
Easiest way when you install is to use the CAD Editor installation. Then you can always downgrade it to a Viewer or Contributor License type on that computer later. Whereas if you just install the Viewer you have to do more work later if you want a different license.
However, it would not be normal to have a variable license type on a given computer, especially for a single user. It would be a bother to switch back and forth on license type (need to restart the computer) - it requires using the Admin Tool, but it is easy.
I think what you want is possible with a "SolidWorks Enterprise PDM Processor License" but those may only be available for large numbers of users.
Maybe you could start out with just some of the Purchasing folks using a Contributor license, and they can be the designated file adders for that department?