I use Livecd to install to hard disk and do full backup(livecd) that i can restore later. This is a great feature. In order to keep Livecd small, some files were removed. Some of them are the Help files. Is there a way to restore them once installed on hardisk?

Nope. One of the various reason we don't recommend a HD installation.

When you add the official 2007.1 update source and install the updates, you get all help and doc files - for the updated rpm's.
Same with new installed rpm's.
A trick would be to un-install stuff, and re-install it.