How to make paper look old but not overdoing it?

try wetting the paper and put it on a baking sheet and "cook" it in the oven until dry.

Totally understand what you mean. I've done a LOT of paper staining in the past few years, as I like the way some of my picture turn out when they look vintage. First off, Paper staining always turns out better when it's done before they're any ink on it. But if you already have something and don't want to re-do it, then we work around it. The absolute best way to stain paper, is with coffee. Since you've already stated that you don't want to use it, then I'll give you some of the next best things. If you make a pot of coffee, then take the used coffee grounds, let them dry a little bit but not all the way and then with your fingers rub the coffee grounds on the paper. Same things with tea, cut a used tea bag open empty it on the paper. A few other ways would be to buy some ink the spray on it, but that gets kind of pricey and doesn't work. If you have a lot of time for this project, then take the paper and put it in a window or somewhere hot where the sun can shine on it. That works like a charm, but takes two to three weeks in best, sunny conditions, and a lot of space if you have a lot of papers. I wouldn't try baking it, it a very tricky process and if not watched carefully can start a fire, plus ruin your paper. If I were you, would use the coffee grounds, and letting the paper sit in the moist coffee grounds is good too. Also, if you want it to look like it was in a book, then make one edge of each page darker than the rest of it. Hope I helped. Good luck! :)