If the bed-wetting is unavoidable due to an incontinence problem then to ensure your dog’s comfort and well-being a good quality bedding designed to allow the passage of urine through it, yet remaining relatively dry on the surface, is essential.
When breeding puppies I have found that Vetbed is excellent, with the properties to ensure puppies remain as dry as possible even when accidents do occur. It can be cleaned in a washing machine, tumble-dried and, though expensive, it will last a very long time.
Absorbent materials such as shredded paper should be avoided unless changed a minimum of once a day, as they soon become saturated and smelly.
If the bed-wetting is not a medical problem, but behavioural, then re-training could be the answer. Diet, exercise or lack of free access to outside could all contribute to the problem.
A thorough assessment of the cause needs to be identified before training begins.