Short answer: you are allowed to do a run up.
Long answer:
PDGA Rule 803.04 Stance, Subsequent to Teeing Off
A. When the disc is released, a player must:
(1) Have at least one supporting point that is in contact with the playing surface on the line of play and within 30 centimeters directly behind the marker disc (except as specified in 803.04 E); and,
(2) have no supporting point contact with the marker disc or any object closer to the hole than the rear edge of the marker disc; and,
(3) have all of his or her supporting points in-bounds.
B. Stepping past the marker disc is permitted after the disc is released, except when putting within 10 meters.
C. Any throw from within 10 meters or less, as measured from the rear of the marker disc to the base of the hole, is considered a putt. A follow-through after a putt that causes the thrower to make any supporting point contact closer to the hole than the rear edge of the marker disc constitutes a falling putt and is considered a stance violation . The player must demonstrate full control of balance before advancing toward the hole.
D. A player must choose the stance that will result in the least movement of any part of any obstacle that is a permanent or integral part of the course.
E. If a large solid obstacle prevents a player from taking a legal stance within 30 centimeters directly behind the marker disc, the player shall take his or her stance immediately behind that obstacle on the line of play. The player must comply with all the provisions of 803.04 A other than being within 30 centimeters directly behind the marker disc.
F. A stance violation must be clearly called within three seconds after the infraction to be valid. The call may be made by any member of the group or an official. When the call is made by a member of the group, it must subsequently be confirmed by another member of the group. A player shall receive a warning for the first violation of a stance rule in the round.
Subsequent violations of a stance rule in the same round shall incur a one-throw penalty.
G. Any throw that involves a validly called and seconded stance violation may not be used by the thrower. Re-throws must be taken from the original lie, prior to subsequent play by others in the group.
H. The player may not retrieve the originally thrown disc prior to the re-throw, except in the case of a putt from within 10 meters. Where a disc is retrieved in violation of this rule, a one throw penalty shall be imposed without a warning.