Perhaps your bifold door has been removed to install new carpeting or just to gain wider access through the doorway, but when it's time to rehang the door in its opening, following a few simple steps can ensure proper alignment.
Stand the unfolded door vertically and parallel to the opening, positioning the pivot side of the door in alignment with the top track pivot bracket.
Raise the door up and insert the door’s top pivot pin into the top track pivot bracket hole, then rotate the door inward to align and insert the door’s adjustable lower pivot pin into the floor bracket.
Move the closing edge of the door to where the guide roller is beside the top track, then depress the guide wheel’s spring-loaded post slightly to insert the roller wheel into the top track.
Measure the distance between the top corner of the door at the pivot side and the face of the door jamb.
Lift the bottom of the door slightly with a pry bar and move the bottom pivot pin in the floor bracket to where the lower corner of the door on the pivot side is an equal distance from the face of the door jamb, matching the measurement determined in Step 4.
Close the door completely and verify that the pivot edge of the door is an equal and consistent distance from the door jamb from top to bottom. Use a level to make certain the door is plumb.