Adding a vertex at an interval to densify an edge
If you need to add many vertices to a line or polygon or a set of selected lines or polygons, use the Densify geoprocessing tool. The tool converts a parametric or true curve (such as an arc, ellipse, or Bézier curve) into a series of straight segments by placing vertices at an interval defined by a maximum distance or angle from the original curve's shape. However, keep in mind that running this tool on a curve that shares an edge with another feature could result in the boundary between them no longer being coincident.
A common use for densification is to maintain a feature's shape during projection or to enable snapping, such as when using spatial adjustment rubbersheeting to align linear features with a different number of vertices.