Official Guidance for ISO 9001?

ISO/TS 9002:2016: Quality management systems -- Guidelines for the application of ISO 9001:2015.

Everyone who is expected to apply ISO 9001 should have a copy of this document. It provides "plain English" guidance on the intent of the requirements in ISO 9001:2015, with examples of possible steps an organization can take to meet the requirements. It does not add to, subtract from, or in any way modify those requirements. ISO/TS 9002:2016 does not prescribe mandatory approaches to implementation, or provide any preferred method of interpretation. It gives insight as to what the authors meant when the standard was written.

ISO 9001 is intended to apply to all types of organizations. However, much of the language is written in such general terms that it becomes hard to understand. This document is issued by the same committee that wrote the standard, so it comes from the right source.

Understanding the standard is also vastly helped by reviewing "ISO-ese" terminology in ISO 9001:2015: Quality management systems - Requirements.