This resource from WebAIM walks users through assessing Word and PowerPoint files for accessibility. Note that the current (2024) instructions describe Office 365, and may not be appropriate for older or more recent versions of Word or PowerPoint.
A web version of the resource is available at https://webaim.org/resources/evaloffice/ and a printable PDF can be accessed at https://webaim.org/resources/evaloffice/evaloffice.pdf
See also the official Microsoft information on creating accessible content in Office at