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As a work-around for the time being you can download the documents from Actionstep to your local workstation and then open them in MS Office. When you have finished editing you will need to replace the version in Actionstep with your locally-modified copy.
You can also rollback the MS Office update if you wish, but we strongly suggest you discuss this with your IT support team before doing so. Instructions on how to rollback the update can be found at https://support.microsoft.com/en-nz/kb/2770432
A list of MS Office versions can be found at https://technet.microsoft.com/en-us/library/mt592918.aspx
We apologise for any inconvenience this may cause you and we are working diligently to resolve the issue. Thank you for your patience.