C182 pilot reported a brake malfunction resulted in loss of control and taxiway/runway excursion and contact with taxiway signage.

Narrative

The problem arose upon landing; when the right brake unexpectedly exhibited only partial availability. The problem was discovered upon landing. Contributing factors were the lack of ability to mechanically slow the aircraft sufficiently to depart the runway to the taxiway as instructed. Focusing on safety and maintaining control of the aircraft became the immediate focus. The goal was to gain sufficient control of the aircraft to avoid an accident; or become a threat to safety. This was accomplished. However; inadvertent movement beyond the initial movement control area resulted. There was minor impact to taxiway markers and/or signs.Once clear of any active areas and clear of other aircraft in the area; a call was made to Ground Control immediately. The aircraft was immediately grounded and a call placed to the local A&P to assess the mechanical issues. Maintenance Chief of the flying club was notified.A request was made to call the Tower and this action was complied with immediately. A call was immediately placed to the local Tower and personal information provided as requested. The issues were discovered and repaired (minor fluid leak resulting in a low fluid level in the right reservoir). The aircraft was safe to return to service and complete the transport mission task safely.Human Performance Considerations. In an effort to comply with local instructions by the Tower; and in light of the unexpected nature of the problem; the ground track was briefly very difficult to anticipate as the aircraft turned to exit the active runway. A focus on safety --moving clear of the active areas-- became the immediate focus; as well as control of the aircraft and preventing any kind additional safety issues. Both were accomplished; however; there was a brief; minor departure from the taxi way; and the aircraft stopped beyond the initial non-movement area.With reflection; had their been any prior indication of the nature of the problem; the landing could have been extended slowing on the runway; and the aircraft taxied off the runway at the end. Quicker thinking in the moment could also have accomplished this. There was an awareness of brisk traffic flow and moving clear of the active is always top of mind in that circumstance. However; safety is a higher concern; and an action that would have extended the landing roll with a safe departure from the runway without deviation would have been better judgement and by far been the preferable decision. It is; of course; possible that items in question could have been overlooked at pre-flight. This produces a decision to renewed vigilance with regard to the satisfaction of safety with regard to ALL aircraft systems prior to departure.The factor affecting this event was the mechanical compromise of a normally reliable aircraft system (brakes) and the unexpected nature of the problem of the right brake not being fully available for braking and steering; while also attempting to comply promptly with turn-off instructions as had been given by the Tower.