The full set of Office Communications Server 2007 R2 documentation is contained in the download file named Communications_Server_2007_R2_Documentation.chm.
IMPORTANT  See Additional Information for important information about circumstances under which a CHM file will not display correctly, and how to resolve the issue.
Selected, high-value sections of the documentation are also provided as separate Word documents for IT Pros who are interested in specific topical areas. Topics covered include:

• New server and new client features
• Planning and architecture
• Deploying Enterprise and Standard Edition
• Deploying specific types of servers and some related technologies, such as load balancers, including Monitoring Server, Archiving Server, Group Chat Server, and Edge servers
• Deploying features, including Enterprise Voice, dial-in conferencing, and Response Group Service
• Upgrading from the Evaluation Edition to a full released version
• Migration from Live Communications Server 2005 or Office Communications Server 2007
• Administering Office Communications Server 2007 R2, Communicator Web Access, and Group Chat
• Backup and restoration
• Security
• Troubleshooting
• A reference guide for using the command-line to deploy and manage Office Communications Server 2007 R2
• A glossary of unified communications terms used in the documentation
• A documentation roadmap

Full list of files

• Communications_Server_2007_R2_Documentation.chm
• Communications_Server_2007_R2_Documentation.zip
• OCS 2007 R2 Administering CWA.doc
• OCS 2007 R2 Administering Group Chat.doc
• OCS 2007 R2 Administering OCS.doc
• OCS 2007 R2 Backup and Restoration.doc
• OCS 2007 R2 Command Line Reference.doc
• OCS 2007 R2 Deploy Monitoring Server.doc
• OCS 2007 R2 Deploying Archiving Server.doc
• OCS 2007 R2 Deploying Communicator.doc
• OCS 2007 R2 Deploying CWA.doc
• OCS 2007 R2 Deploying Dial-In Conferencing.doc
• OCS 2007 R2 Deploying Edge Servers.doc
• OCS 2007 R2 Deploying Enterprise Edition.doc
• OCS 2007 R2 Deploying Enterprise Voice.doc
• OCS 2007 R2 Deploying Group Chat Server.doc
• OCS 2007 R2 Deploying in a Multiforest Topology.doc
• OCS 2007 R2 Deploying Monitoring Server.doc
• OCS 2007 R2 Deploying Response Group Service.doc
• OCS 2007 R2 Deploying Standard Edition.doc
• OCS 2007 R2 Getting Started - Documentation Roadmap.doc
• OCS 2007 R2 Getting Started - New Client Features.doc
• OCS 2007 R2 Getting Started - New Server Features.doc
• OCS 2007 R2 Getting Started - Technical Overview.doc
• OCS 2007 R2 Getting Started - Unified Communications Glossary.doc
• OCS 2007 R2 Migration from 2005.doc
• OCS 2007 R2 Migration from 2007.doc
• OCS 2007 R2 Planning.doc
• OCS 2007 R2 Preparing Active Directory Domain Services.doc
• OCS 2007 R2 Security.doc
• OCS 2007 R2 Supportability.doc
• OCS 2007 R2 Technical Reference for Clients.doc
• OCS 2007 R2 Technical Reference.doc
• OCS 2007 R2 Troubleshooting.doc
• OCS 2007 R2 Upgrading the Evaluation to Full Released Version.doc
• OCS 2007 R2 Walkthrough - Mediation Server Replacement.doc
• OCS 2007 R2 Walkthrough - Scale to Load Balanced Edge Server.doc
• OCS 2007 R2 Walkthrough - Scale to Load Balanced EE Pool.doc
• OCS 2007 R2 Walkthrough – Small- to-Medium Business Deployment.doc
• OCS 2007 R2 Walkthrough - Voice Deployment.doc

Downloads:
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=e9f86f96-aa09-4dca-9088-f64b4f01c703