Is this something that you have seen in notes following a meeting?
Shorthand phrases such as Michael to share the document are a standard formula in the 'actions' sections of meeting minutes.
This is an abbreviation of 'Michael is to share the document' : note that this <em>is to, </em>not <em>has to.</em>
The construction <em>subject + be + to + infinitive </em>is one of the many future forms which we have in English. We use it in formal contexts to mean that this is the course of action that has been agreed.
NB You will see this abbreviated construction very often in news headlines. For example, this headline:
Prime Minister to announce new regulations next week
is the standard shorthand for:
The Prime Minister is to announce new regulations next week
-meaning that he is scheduled to do this.
I hope that helps.