Acidity in coffee is a complex topic.
Acids yield flavor, literally by donating protons to receptors on the tongue, and coffee beans are packed with a range of acid compounds from many families: citric, malic, chlorogenic, quinic, etc. In that sense, the perception of flavor in coffee is an exercise of consuming the various acids that yield taste.
When we talk about whether coffees have high acidity, we're really talking about whether the taste profile has distinct peaks (for example, floral or fruity), as opposed to a flatter flavor profile. And typically, coffees either grown in richer, volcanic soil, or those grown at higher elevations, feature taste profiles that are what we'd call peak-ier.
But there's also a misperception that acidity in coffee is synonymous with how acidic a coffee is, i.e. what the pH is. pH, or hydrogen potential, is a measure that indicates how base or acid a substance is. And the greatest determinant in the pH of brewed coffee, since it makes up 99% of what we consume, is the water we use to brew.
If you want low acidity coffee, seek out Brazilian and El Salvadoran origins. But if you're looking for a less acidic cup, use neutral pH, filtered water.
More to the point, if less acid is what you're going for, brew methods play a big role: any immersion-based extraction (think aeropress or french press) tend to leave coffee particulate in the final brew. In the stomach, the extraction process will continue, and in many people this tends to encourage the stomach to produce more gastric acid.
My best suggestion: select flavor profiles you enjoy, independent of their relative acidity, and make sure you brew with water that won't distress your tummy!