Simple:

Changing and Replacing reference numbers, lead lines, figure numbers, figure order, headers, and page numbering

Moderate:

When ever any new drafting takes place, such as reorganizing flow charts, making a disclaimed are claimed, shading adjustments, removing minor features from a utility illustration, adjusting fills in cross sections

Complex:

When ever large amounts of new drafting is need, such as adding claims to a design illustration, moving parts or features, adding shading to figures, replacing stipple instead of line shading, modifying detailed utility figures,