Good Morning,
From what I have read arm pain is not a common symptom of GERD (gastroesophageal reflux disease), although it can occur in rare cases. In general, GERD involves the reflux of stomach contents into the esophagus. While many people have no symptoms, heartburn is the most common complaint. However, other patients have more atypical symptoms such as chest pain, which can mimic heart attack; and sore throat, hoarseness, or a bad taste should stomach contents reach the mouth.
You are perhaps experiencing an atypical sx. Do check with your physician if this is causing you a great deal of concern or you have any questions re the arm pain just for you own peace of mind.
Take care,
Kitt