At first blush, copying a workflow seems like a time-consuming manual process of re-creating a workflow by re-entering it into CRM.  But there is a very simple option.

As you probably know, you can create a workflow as a normal workflow, or as a workflow template.  When you create a workflow template, you can easily use the template as a starting point to creating more workflows.  What you may not have known is that your existing workflow can be saved as a template - then you can use the template to make copies. 

Here's the process:

(1) Open the workflow that you want to copy.

(2) Unpublish the workflow (careful: if the workflow is in production, you may want to make sure that all open instances of the workflow have completed running and that the workflow will not be needed for the next few steps - best to do this between the hours of 1:00 am and 3:00 am )

(3) Convert the workflow to a template.  This is accomplished by opening the unpublished workflow, and selecting "Workflow Template" for the field titled "Publish As"

(4) Publish the template: Before you can use the template, you have to publish it.  You publish a template in the same manner that you publish a normal workflow (i.e. click the "Publish" button).

(5) Create a new workflow.  Use the template you just created to create this new workflow.  If you wanted to keep your old workflow running while you develop a new one, then go ahead and publish this new one immediately - and then create another new workflow that you will use to make your changes.