You should be able to open these documents in Google Docs, OpenOffice, Apple Pages, or MS Word without trouble. They are unlocked, so you can add your own graphics, change colors, and update them to make them branded to you.
Due to the generic file type, there may be some formatting necessary to make them appear as you wish on your own word processor.
Grandstream GXW Series BYOD Guide
Yealink Device Training Video: