It's not ever illegal, as long as it's your physical copy. Is it unethical? Well if you're censoring your copy, clearly not: you still saw the ads.

But are you asking in good faith? Or are you asking because you want to get to a point where you use a service that costs money to maintain and yet you don't spend money or view ads but you still feel ethical?

A lot of ad people would say that's unethical. Of course, a lot also say it's unethical to go to the bathroom during TV ads instead of sitting there and watching them like a good little consumer.