APP 11.1 M030 includes a pretty comprehensive built-in line numbering feature. However this doesn't work well for multi-column pages because placement of line numbers can only be "left" or "right" (of line/column/frame/etc.). The most common requirement this misses is for double-column pages where line numbers appear to the left of column 1 and to the right of column 2. The simplest implementation I can think of is a third option called "outside". This would place the line numbers on the outside of the column. Inner columns (e.g. for 3 or more column pages) should simply respect the column ordering, such that for left-to-right frames the inner frames have their numbers on the left, for right-to-left (arabic) frames the inner frames place their numbers on the right.