Highlighter ink compositions can be prepared which provide improved abilities to reduce smear during highlighting. Highlighter ink compositions can include an acid buffer having a pKa from about 2 to about 6, a highlighter colorant, and a liquid vehicle. The image for highlighting can be formed on the substrate using any conventional printing technique, such as ink-jet printing or other printing techniques. Application of the highlighter ink compositions of the present invention to a printed image results in a reduced degree of image smear, particularly when the image was produced by an ink-jet printing process. Further, the acid buffer can be configured for reducing mobility of specific ink-jet colorants. In this way, the highlighter ink composition can be specifically tailored for reducing smear of various printed inks.