Duplicating, or "duping" items has been around for as long as PC RPG's, and allows you to use glitches to duplicate your items in the game. This video will teach you how to use the stunningly easy-to-use dup glitch in Dragon Age 2 to duplicate as many of any item you have 2 or more of your want, up to 999. This essentially gives you unlimited money and items.
From the Creator:
1.) Move the items you want to duplicate to Junk (Y Button). You can only duplicate only one set of items, any other will simply be sold, so move only one set in this step .
2.)Next, go to a merchant and choose to sell.
3.) Sell the whole stack.
4.) Now go to buy ,and then select buyback. Purchase ALL BUT ONE of the items back.
5.).Go back into the Sell menu and go to the Junk tab.
6.) Select the item stack. Here comes the tricky part... Press Y and A at almost the same time. The item will disappear from your junk list, but a Sell prompt should still appear.
7.) Now go back to Buy/Buyback and you will notice that the quantity of the items the merchant has are doubled. Repeat steps 4-6 as many times as you like for infinite gold and stacks of items up to 999.