The ornamental design for a decorative memorandum, as shown and described.
FIG. 1 is a front elevational view of a decorative memorandum showing my new design;
FIG. 2 is an enlarged perspective view of the penholder for the decorative memorandum thereof;
FIG. 3 is an enlarged elevational view of the calendar for the decorative memorandum thereof; and,
FIG. 4 shows a perspective view of a decorative memorandum made up a frame comprising an opened case for insert the letters, a penholder, a device for stick up the hour, a memo pad, a second opened case for hang up the keys, and a diary for each month.