From the documentation it's not clear whether --limit-rate applies to upload (i.e. sending the request) or download (i.e. receiving the response) or both.
Intuitively, I'd be inclined to guess it applies to upload, as i can hardly even imagine how a rate limit could be applied to download (given that it depends on the other side). However, there's this note:
If you also use the -Y, --speed-limit option, that option will take precedence and might cripple the rate-limiting slightly, to help keeping the speed-limit logic working.
and since speed-limit is related to download speed, that is confusing.