To do a full bust adjustment without affecting the rest of the bodice, draw a first line from the shoulder to the hem going through the apex. This line must be parallel to the grainline.
Draw a second line from the apex to the middle of the bust dart.
Draw a third line from the apex to the armhole, about 1/3 from the tip of the shoulder.
Draw a last line perpendicular to the first one at the tip of the dart waist.
Cut the line starting from the hem, passing by the apex and ending at the armhole leaving a notch. Cut out the line in the middle of the bust dart keeping a notch at the apex.
On another piece of paper, draw two lines parallel spaced at half of the measure you want to increase (If you need to increase the bust by 4cm. in total, you need to space the two pattern pieces by 2cm). Paste the pieces along these lines starting from the centre, then aligning the side.
The middle part is shorter than the side. Cut along the fourth line traced at the begining. Redraw the centre front and the waist.
Align the centre part to the waist line of the side and the centre front. Paste all the pieces on the paper.
Redraw the darts, then redraw the side and the waist with the darts closed. Redraw also the armhole.