National Rifle Association Chief Executive Wayne LaPierre billed the group’s ad agency $39,000 for one day of shopping at a Beverly Hills clothing boutique, $18,300 for a car and driver in Europe and had the agency cover $13,800 in rent for a summer intern, according to newly revealed NRA internal documents.

The documents, posted anonymously on the internet, provide new details of the clothing, travel and other expenses totaling more than $542,000 that Ackerman McQueen Inc. alleges Mr. LaPierre billed to it.

The...