Translation of Documents

Hi.

It so happens that a number of documents regarding our spouse visa application need translating. For example:

1. Marriage Certificate
2. House Sale Contract
3. Certain Bank Statements

In this sense, I was wondering how the translations should be structured. Does every document/collection of documents need to have a separate cover letter/signature explaining that it is a translation of the original etc? Or, can the certified translator just translate everything and offer a single cover letter stating it was a translation of the original. We will be uploading everything, so I wanted to ask you what the best way to present these separate translations would be.

Thank you!