I want to download Ubuntu 12.04 LTS windows installer in part because I have small download limit for a month. How do I do that?
If that is the case select the torrent version for download and throttle your torrent.
Here are the desktop links to the torrent:
You can also stop the download at any time and continue it when ever you want.
Depends the client, but µTorrent has an option to set a Transfer Cap:
Only change limit Type to "Downloads", set the Bandwidth and the Time Period.