A family of Microsoft word processing software products for creating web, email, and print documents.
This fixed line numbering is traditional for legal documents (using specially printed "pleading paper" such as you can see at http://www.blumberg.com/invoice.cgi?rm=view_cluster;cluster_id=398483), and the "line numbers in a text box in the left margin" solution is one that was originally provided by the Pleading Wizard in older versions of Word. Word's automatic line numbering was not a suitable solution for older secretaries, typewriter-trained, who pressed Enter twice at the end of a paragraph. Although the fixed line numbering does not adjust for variations in line spacing, this is evidently not an issue in at least some types of legal documents. If you google for "pleading paper," you'll find a host of templates and macros to replicate the effect of printed pleading paper.