Depends what is meant by "low".
7.0 is neutral. Higher is alkaline, lower is acidic.
If you're between 5.5 and 6.5, praise Gaia. Most garden plants will thrive.
If it's lower than that, there are still plants that will do well. Blueberries love freakishly acidic soil. And as the other poster mentioned, potatoes get less scab problems if grown in acidic soil.
DON'T add lime unless you know what your ph is. I mean, a number, not just "low". And don't try to change it if it's still within range of most garden plants' needs.