Despite a number of employees standing around doing nothing in the nearly empty store, I was told that no, they couldn't help me.
"Why not?" I asked.
"It's against store policy."
I limped back to my car and drove to Staples, which is a little out of my way, but where they were more than happy to help me. A very nice clerk went and picked up a case of paper and brought it to the customer service desk, where a manager not only checked me out but found a coupon for the paper, and the clerk carried it out to my car.
I went home and called Office Depot customer service, and was told that it is certainly NOT against store policy to refuse assistance with carrying merchandise to the check-out and out to the parking lot for a disabled customer.
Needless to say, I will not be visiting that Office Depot again even if it is conveniently placed on my way home from work.