You may use the Settings -> Text Template menu to store MS Word documents as templates for serial letters. These templates must have the .doc format and can get created by using the Office Plugin extension available at the CRM’s Help menu. This extension links Word and the CRM and provides the CRM fields to Word to be included as merge fields.
If you do not want to use the Office Plugin because it is not compatible to your Word version or to inconvenient you may edit templates directly. For this you need to understand Word’s concept of merge fields as it is used for serial letters. For the most common fields such as addresses you may download a sample document Word Tempate Sample for the use with CRM’s Contacts or Leads. If you need other fields please contact crm-now.