Proofreading

Proofreading is reading a printed text for the purpose of detecting typographical errors and marking it with handwritten proofreader's marks for correction.

A modern alternative is reading the text on a computer display in wysiwyg form and entering the corrections directly into the computer.

External links:

Examples of proofreader's marks: http://www.ruf.rice.edu/~opa/pubs/ed-style-guide/proofread.html