The way you could accomplish this would be using "skip logic" to hide that required field unless something else is selected. If you need to have the field exposed regardless but only require it based on an answer to a previous question you can have two instances of the field, one required and the other not and show the right one based on the answer to another question.
Here is some information on Skip logic which is a paid feature: https://www.acrobat.com/formscentral/en/library/skip.html
Thank you for the help. I'll start reading and testing. How often does Adobe add to the list of selectable Actions? The Action of creating conditionally required fields would seem an logical, since this is already an Adobe field attribute. I'm having to convert from Microsoft Infopath forms to Adobe forms per my I/S dept directive and with zero training. Infopath allowed me to create a conditionally required fields by selecting a feature, without having to create multiple fields and code.
We prioritize new features in a variety of ways, no schedule of when something like that could happen.
We do have an "Ideas" page where customers can add and vote on feature requests:
If you cannot find an existing request and need to add a new idea, please go tohttp://forums.adobe.com/community/formscentral and click on "Submit Feature Request" link under Resources section.