Even though you have checked out your document in Evolve you still can't edit it when opened.
This could be related to a Microsoft Word setting the opens your document in Preview mode, Protected View or Reading View.
Turn off preview mode:
In Microsoft Word:
1.Go to File->Options->General
2. Under 'Start up option' - untick 'Open e-mail attachments and other uneditable files in reading view"
If Documents are still opened in a read only mode, you may also need to change the Protected Mode settings:
1. Go to File->Options->Trust Centre->Trust Centre settings->Protected View.
There are 3 options here that open documents in preview/protected mode.