Scrutinise the document and see how it was laminated in the first place. One of the methods to laminate a document is to place it in between two plastic sheets. The plastic sheet is then sealed on all four sides. Removing such a lamination is easy. All you need to do is to carefully cut off the sealed sides and remove the lamination.
The second most commonly used method of laminating a document is to place it in between two plastic sheets and then pass the sheets along with the document between heated rollers. Doing this makes the plastic sheets firmly adhere to the document. Removing this sort of lamination is relatively difficult.
You need to heat the lamination in order to loosen it. A heated steam iron has to be used for this purpose. Of course directly heating the lamination with steam iron would not be a good idea because the lamination may burn. To avoid such an outcome, cover the laminated document with a towel or a piece of cloth. The towel or cloth you use to cover the laminated document should be the width of a pillow case.
Let the steam iron heat up but make sure that it does not burn the towel or cloth covering the laminated document. Moreover, the lamination must not curl due to the heat of the steam iron.
Iron the towel or piece of cloth for a few minutes. Heat from the iron would loosen the lamination. Set aside the heated iron and try peeling off the lamination carefully. If it does not come off, cover the laminated document with towel or cloth once again and reheat it, a little more than before. Try peeling off the lamination again.