Can a person have pain with an abdominal aortic aneurysm before it actually ruptures?

Possible: There is a condition called a "contained rupture", which means the walls of the aorta have been violated however the leak is contained. This is certainly painful but is not a full blown rupture. Urgent repair is indicated. A ct angiogram helps to identify this.

Yes: If you have an aneurysm and you have pain you should immediately go to the nearest emergency room. This could be a sign of impending rupture or rupture. This is an emergency.

Pain w/o rupture?: At times a contained rupture can allow someone with a lot of pain to put off, temporarily, the big catastrophe. This is an urgent situation at that point which generally requires immediate attention.