The noun documentation can be countable or uncountable. In more general, commonly used, contexts, the plural form will also be documentation. However, in more specific contexts, the plural form can also be documentations (very rare) e.g. in reference to various types of documentations or a collection of documentations.

Is there such a word as documentation?

documentation | American Dictionary

Documentation is also the process of providing proof for the things you write about and naming the texts that you use.

What is the difference between documentation and documentation?

Document is a form of information that means record,or a capture of things and events so information will not be lost. But the process of to save, to improve and make essential is documentation. In IT especially we tend to use documentation as a plural for document.