Is SharePoint prompting your users to login when they are in the office or opening documents from SharePoint? There are a couple of things you can try:

1- Added SharePoint site to Intranet Zone

On the Users Internet explorer go to:

• Tools > Internet Options
• Select the Security Tab
• Select the Local Intranet zone then click Sites
• Click Advanced
• Add the SharePoint URL then click OK
• Click on Custom Level then scroll to the user authentication section at the bottom
• Set it to Automatic logon with current user name and password

2- Registry

Adding this entry allows the users login to be forwarded to the server you specify.

• Open Regedit
• Navigate to: HKLM\System\ControlSet001\services\WebClient\Parameters
• Add a new Multi-String Value: AuthForwardServerList
• Data: http://sharepoint.domain.local
• Reboot