The ornamental design for a surface pattern for an absorbent article, substantially as shown and described.
FIG. 1 is a top plan view of a surface pattern for an absorbent article, the dotted line being for illustrative purposes only and forming no part of the claimed design;
FIG. 2 is a second top plan view of the surface pattern for an absorbent article, the dotted line showing an alternative disposable absorbent article being for illustrative purposes only and forming no part of the claimed design; and,
FIG. 3 is a third top plan view of the surface pattern for an absorbent article, the dotted line showing an alternative disposable absorbent article being for illustrative purposes only and forming no part of the claimed design.