Do you use external documents? External documents are those generated and (usually) updated by organizations outside your company. Documents such as government standards, MIL-SPEC documents, Federal Aviation Regulations, drawings created by your customers or vendors, etc. are considered external documents. Chances are your organization is not responsible for, or allowed to, modify external documents.
If you don’t want to control external documents, you must specifically state in your quality manual, and on the documents themselves, that they are “For Reference Only” and are not updated.
External documents that you depend on, and are updated occasionally, must be controlled in your quality management system. Revision is usually controlled by the publisher. You are responsible to ensure that you have a means to receive updates from the publisher (such as a current subscription) and that you periodically check to make sure that you have the latest revisions.
As part of your document control, you must also devise a way to withdraw the obsolete documents and prevent their accidental use, and also issue the new updated documents to the necessary personnel in your organization. Whatever process you use to make sure you have the latest revisions, you must document this in your quality manual.