anybody have experience with ipad—a reader is having download troubles…

I'd like to be able to answer him. He got the file down onto his computer (mac, perhaps)—and we're thinking it's because it's a huge zipped file. Don't know if he's unzipped it. The IPad couldn't download it. He's using Safari.

Anybody know what format is best for the IPad? Hints, clues, worldly wisdom?