Haritaki is very helpful in assisting indigestion

The cause of indigestion in Ayurveda is an imbalance in your physical/emotional/mental set up called Vata.

Vata is an imbalance in your body that shows up in the mental set up as worry and stress and concern. This in turn causes digestive issues such as gas, stomach ulcers, and digestive related diseases including the indigestion listed above.

Haritaki helps the indigestion Vata condition by increasing the activity in digestion, by removing toxins and debris. Haritaki also helps with brain function which freuently leads to a decrease in patterns such as stress and worry.

Here is a great description of Vata issues:

Source: https://www.mapi.com/ayurvedic-knowledge/doshas/vata.html

Vata out of Balance

Prana Vata: Worries, overactive mind, sleep problems, difficulty breathing.
Udana Vata: Dry coughs, sore throats, earaches, general fatigue.
Samana Vata: Slow or rapid digestion, gas, intestinal cramps, poor assimilation, weak tissues.
Apana Vata: Intestinal cramps, menstrual problems, lower back pain, irregularity, diarrhea, constipation, gas.
Vyana Vata: Dry or rough skin, nervousness, shakiness, poor blood flow, stress-related problems.

How to take haritaki to reduce indigestion

I recommend you start with haritaki capsules, many people cannot stomach haritaki in powder form
Take one capsule with each meal, after food with water or juice
Monitor the effects and increase the amount if you feel no effects.
If you find that the capsules are helping you, I recommend you open a capsule and taste the powder
if the powder is easily digestible for you, then consider buying the powder in future. The powder has more uses such as using it as a mouthwash and using it on the skin.
You can also get dried whole haritaki and soak them, and make a tea from the juice.

This link takes you to more benefits

Other ways to help indigestion

Indigestion causes

Drugs often affect the digestive tract
Alcohol
Cigarette smoking
Eating too much rich food causes the digestive tract to be clogged
Overeating in general
High fat foods, slow down digestions
Medications including aspirin, which irritates the stomach lining, and oral contraceptives which have a similar effect.

Habits that reduce indigestion:

Avoid drugs and alcohol, which irritate the stomach
Reduce over eating by taking smaller amounts of food throughout the day
More movement in general
Yoga exercises the abdomen which massages the intestinal organs. It also calms the whole body so works on the stress factors.