You can lay a memory foam topper on top of your existing mattress to make your bed softer. This is particularly useful if your existing mattress is too firm. However, if your mattress is too soft for you already, a topper or memory foam pad will only make it softer.
The problem might be your pillows. If your mattress is okay, but your shoulders and neck ache when you wake up in the morning, it could be that your pillows are not as supportive as you would like them to be. There are two types of memory foam pillow available. One is a pre-formed shape that is used on its own. The shape is such that it fits into the curve or your neck and supports your head. It comes with a fitted cover but will also fit into standard pillowcases. My mother suffers from cervical spondilitis that causes her a lot of pain in the base of her neck and shoulder. My sister bought her a shaped memory foam pillow and once she got used to it, found it helped her to sleep comfortably. She now sleeps with nothing else. You only need the one pillow for the correct amount of support. Pillows are available in the normal pillow shape but they are slightly more expensive because they use more foam and are not likely to be as supportive.
Memory foam pillows and toppers are made from the same high density visco-elastic foam that the tops of the mattresses are made from. Density makes a difference to how soft the foam is - 4lbs per cubic inch is softer than 5lbs (Tempur Pedic ® use 5.34lbs density foam). The toppers come in varying depths but the standard is 2" to 3", the same amount as would be found in full mattress construction, over a harder supportive layer of foam. Memory foam is too soft to be used on its own in a mattress. As for cost, the less dense the foam, the cheaper it is, but to get the best benefit, it is recommended to not use a density of less than 4lbs per cubic inch.
