The AS9100 Rev D standard does not talk specifically about this issue, and only states in clause 7.5.2c (creating and updating) that documented information is reviewed and approved for suitability and adequacy, and leaves the decision on how to do this appropriately to the organization. In fact, with a small organization you may have only one expert in a certain process so that there is not an adequate review person available (AS9100 is written for all types of organizations). That being said it is difficult to see how one person could review their own work, and a second person review can be very helpful to highlight potential issues in a document.
It is important to remember that this clause only talks about QMS documented information, and not the information covered by clause 8.1.2 for configuration management which deal with control of physical and function attributes of the products or services which often include drawing, specifications, etc. In the end it also comes down to what customer and legal requirements are imposed on you for approval of certain documentation, so make sure you consult these requirements also.
For more information on understanding the AS9100 documented information clause, see this article: A new approach to document and record control in AS9100, https://advisera.com/9100academy/knowledgebase/new-approach-to-document-and-record-control-in-as9100/