There are two kinds of proper paperbacking. One involves mounting a one-sheet (or any other poster printed on thin paper) on Japanese rice paper only (think linenbacking without the linen). If done by museum people or the very best pros, the paper is deacidified and stabilized, and restoration is done to "voids" (areas of paper loss) only.
The other involves removing the top layer of a half-sheet, insert, window card or lobby card (or any other poster or lobby card-type item printed on thick paper) and mounting it onto a heavy board backing, and then performing full restoration to the item.
You couldn't do much restoration to the first type if you wanted to because it only has a very thin layer of rice paper behind it. The second type is now on a heavy board, so all sorts of restoration can now be performed.
And of course there are many not-very-talented restorers who attempt to imitate both types of above paperbacking, but in restoration, you absolutely get what you pay for, these not-very-talented restorers charge less and deliver much less.
Incidentally, the second type should be called "board backed" which would end the confusion, but most collectors hear "board backed" and think "mounted on board" so people don't use it that way for that reason.
Bruce