This is a complex question I often get from customers. The answer is both yes and no.
You can pitch a gutter but you must first understand the anatomy of a properly installed pitched gutter. A hanger hooks onto the front of the gutter and is attached in the back by tightening the screws or nails against the fascia. In that process, holes are created in both the back of the gutter as well as into the apron.
When you move a gutter down to create a better pitch, the new nail hole is typically lower than the original hole.
These additional holes create leak points during heavy flows and the water can get behind the gutter and rot out the soffit and fascia.
So should you repitch your gutters? No.