Thanks, Stefan!

That's indeed the way to do it. However, after I follow the precedure and the line numbers are inserted on the part of the text I selected, the part that was not selected moves either to the page above or the page below, depending on whether the non-selected part of the text is above or below the selected text. Does anybody know how I can avoid this? To show you more concretly what happens when I insert the numbers, take a look at page 2 of this document http://www.cespe.unb.br/concursos/DI...Br11_02_01.pdf . After inserting the line numbers on the left side of the text of the left column, the headings above the text ("This refers to..." and "Godzilla's...") would move to the page above, and the righ column would go to the page below. Thus the only thing left on the page would be the text with the line numbers.