This problem is still unsolved. I followed the global handler (DocumentEvents.Insert.After) road and this is my code (the interesting parts):
var currentStep=e.Node.WorkflowStepName; // it's strange, but this results in "published"
var newStep=e.Node.MoveToNextStep(); // this results into "published" step as well.
However, viewing the document in the Pages app shows it's still in the Edit step. I also tried the code from the previous post and some other variants, but all returning the same result. In general I ask me why e.Node.WorkflowStepName returns "published" though in Pages it shows "edit"?