The pressure reading will be higher if held to low and lower if held too high.
Work Step by Step
When blood pressure is measured, the doctor tries to measure the pressure of the blood being pumped by the heart. If the cuff is held below the level of the heart, the measured pressure will be too high: it will measure the pressure of the blood pumped out of the heart plus an excess pressure due to the cuff being below the heart (much like the pressure in a swimming pool rises with increasing depth). By a similar argument, if the cuff is held above heart level, the measured pressure will be too low.