Trade Up generally defines a strategy where retailers and manufacturers want to shoppers to spend more on their usual products. For example, if they generally buy a rice at 1 USD per kilo, it would correspond to make them buy a rice at 1.15 USD per kilo. Trade Up could be summarised as “1 $ More”. It usually focuses on existing shoppers of that category.
A trade up strategy can be done through premium added to the upper price level product of the range.