Document Record approval rules with different conditions depending on who submits it

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Hi, I'm looking for some help configuring Document Record approval rule. The requirement is that for certain Document Types e.g. 'sickness certificate', if the employee submits the Doc Record, it goes to their line manager for approval (based on supervisor hierarchy); but if their line manager or HR Specialist submit the Doc Record for their employee, it is auto-approved. I've seen from release 19D that this is possible, but not sure how to do it. If anyone can give me simple instructions or point me towards where to find existing step by step guidance, I'd be very grateful.