We will/would also promote ABC Business during our event.
Do I use will or would in the above sentence?
Depends on how certain you are.
http://home.comcast.net/~garbl/stylemanual/vthruz.htm
see will/would
i am pretty certain.
So it's not about the tenses? present or past?
No, it is not about tenses at all. It is about certain or conditional action. Look at that site.
The word "will" says that the action is going to be done in the future. No doubt about it.
The word "would" says that the action might be done in the future -- possibility, but not a certainty.
To determine whether to use "will" or "would" in the given sentence, you need to consider the context and the verb tense being used.
If you are talking about a future event that is certain to happen or a plan that has been confirmed, you should use "will" in the sentence: "We will also promote ABC Business during our event."
On the other hand, if you are talking about a hypothetical or conditional situation, or expressing a polite request, you should use "would": "We would also promote ABC Business during our event."
Without additional information, it is not possible to determine with certainty which verb form is appropriate in your specific case.