Will adding more sugar to a dough recipe negatively impact the outcome?

As Cynthia says, depends on the recipe, but I find that if you add much more sugar than the recipe calls for, it really can affect the texture of a loaf or leavened cake, and it can get very heavy and dense. One idea that I came across recently and which worked brilliantly is to add crushed sugar cubes to the dough when you put it in for the final rising - you'll get lots of little sweet spots in the dough, and can be fairly sure that the dough will rise properly. Otherwise, you can (1) have a look for a recipe that calls for more sugar, as it should work properly, or (2) brush the loaf with sugar syrup for some extra sweetness.

You can certainly increase the sugar a bit, but without knowing what kind of dough you're making, it is difficult to guess the appropriate amount. By adding sugar, you are essentially super sizing your dough's fast food component. Yeast cells will gobble up sugar readily and begin reproducing rapidly; if you increase the sugar, you will send them into overdrive and risk over-proofing your dough because by the time the yeast population begins to break down the starches in your flour into simple sugars, there is already such a huge population that there may not be an adequate food supply for them. The best way to counter that effect is to also boost the salt in your dough. Salt competes more effectively than yeast for water at the cellular level, so it essentially rations the amount of water critical for yeast cells to reproduce. If you increase you sugar by 10%, also increase the salt by the same percentage.