You can't print more gold, but you can mine more, and release more onto the market if you want to undermine the price of gold. Likewise, you can restrict the supply of gold by mining less, forcing the price to rise.

That's just as good as printing more money: no - it's better. And it is already being done. The major gold producers limit the amounts of gold they produce to meet their economic and political requirements (or those of their masters).