SQL Error [42883] - function does not exist - Cannot call function from trigger
As the documentation says:


  The trigger function must be defined before the trigger itself can be
  created. The trigger function must be declared as a function taking
  no arguments and returning type trigger. (The trigger function
  receives its input through a specially-passed TriggerData structure,
  not in the form of ordinary function arguments.)


The function you have declared is:

insertIntoAutoIncrementExample(companyname text,location text) ... returns void


so it does not fit both in the return type and in the argument types.
A trigger function does not take arguments but can access the values inserted or changed in the row variables NEW and OLD. They get automatically defined in plpgsql, see Trigger procedures in the plpgsql chapter for  details and examples.

Concerning the error message:

function insertintoautoincrementexample() does not exist


it means: this function name, with an empty list of arguments, does not exist.
The presence of parentheses around nothing is relevant, because in postgresql, functions always go with their argument types:
foobar(int) is not the same function than foobar(), or foobar(int,int) or foobar(text).