Hello,
Alfresco includes libraries such as Apache Tika, which are able to extract data from documents such as the metadata / custom XML in Office documents. As far as I know, Apache Tika also provides components to embed data back into documents although I am not sure if the necessary Tika version is already included in Alfresco or if this covers Office metadata / custom XML yet.
As an open platform, you can always add other libraries such as docx4j, which we use in several customer projects to read and generate Office (OOXML) documents.
Regards
Axel