Use tracing paper over the nested dress pattern to make a single pattern in your size. Cut out the patttern.
Lay the cut out pattern over tracing paper, newsprint, or any large sheet of paper. Using a ruler, draw a straight line across the bottom of the pattern, approximately 10 inches (25 cm) from the bottom edge.
Cut the pattern in half, using the line as a guide, and separate the two pieces. The distance between the pieces will determine the increased dress length. Bear in mind that the hem will take up approximately one inch (2.5cm).
Tape down the two pieces to your sheet of paper. You will use this to trace out a new pattern.
Make adjustments to the bottom edge and side. Use a ruler to carry on the line, making sure the two meet and form a right angle. Carry on tracing the rest of the pattern. Remove the tape and the old pattern. Cut out your new pattern, being sure to write the size and the fold and grain lines for future reference.