If you're okay with windows phone, you can try Lumia 510, the most affordable lumia and can open any office document as it includes a dedicated office reader

Else, Just look for any symbian phone that suits your budget and every one will be able to open documents quite easily. Don't go with any asha device. They will never help you with your purpose
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Die hard Nokian, willing to help other Nokia Users.
Current Handsets - Lumia 900, Nokia 311, Nokia C3-00, Nokia C1-01, Nokia 6500-s.