From Jan Tielen's blog:

The BizTalk team has kept it's promise, the documentation and SDK updates are available! Additionally, the Installation Guide and Orchestration Designer for Business Analysts (Visio Add-in) are also published today.

• BizTalk Server 2004 Product Documentation
  Download the updated product documentation Help file to have new content for BizTalk Server 2004 on your desktop. The production documentation is updated on a quarterly basis.
• BizTalk Server 2004 SDK Refresh
  The BizTalk Server 2004 SDK Refresh contains updates and additions to samples, utilities, headers, and other developer artifacts to aide in the development of BizTalk Server 2004 applications.
• BizTalk Server 2004 Installation Guide
  Learn how to install BizTalk Server 2004 on a single computer or on multiple computers, with the information in this document.
• Orchestration Designer for Business Analysts
  Visio Add-In that enables Business Analysts to create business orchestrations that can be implemented using BizTalk Server 2004.