NVDA has a series of ebooks on many of the Office products (Word, Excel, Power Point, and Outlook). While these trainings are focused on using these products with the NVDA screen reader, many of the shortcut keys and subject areas are described such that they can be applied using other screen readers. Each tutorial costs about $25 US and there are even bundles that lump these materials together along with technical support. Below is a link to the Word training.
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Sample chapters are available for free via a link on the above mentioned page so you can see the style of the training.