Here are documents of workflow on SAP
General Logistics Workflow Scenarios
Integration with SAP Business Workflow
Real Estate Management: Workflow Scenarios
Sales and Distribution (SD) Workflow Scenarios
Treasury: Workflow Scenarios
Cross-Application Components: Workflow Scenarios
Materials Management: Workflow Scenarios
Find below step by step SD user guides
Availability Check Sales
Availability Check Shipping
Billing Creation
Billing Plan
Complaints and Returns
Customer
Contents
Purchase Requisitions – Customizing your Desktop Settings
Favorite SettingS
Personal Setting
Default Settings for Purchasing Screens
Creating A Purchase Requisition Use Transaction ME51N
Section 1 ~ Header
Section 2 ~ Item Overview
Section 3 ~ Item Detail