In order to view documents, the user must have access to Access Document Management (ADM), and have the relevant permission set in their accounts security profile.
To do this, head to Access Evo and give the user either of the Web access role types from the members area:
An approver from Access Financials will have the permission set as default and so should now be able to view the documents in Approve.
An approver from Dimensions will need the the Documents option enabled from within their security profile. This can be found under Invoice Register, Transactions.