Summary:

You may find when carrying out mail merges within CRM that you do not always have full address information for a person or company record and that blank lines are then added to the merged document due to the missing data.

To ensure that when the merge process is completed that blank lines are not merged you will need to add a carriage return after each address merge field. This will ensure any blank merge fields will be omitted.

References:
https://community.sagecrm.com/userhelp/Content/User/MD_CreateNewWordTemplate.htm

https://community.sagecrm.com/user_community/m/cloud_documentation/27200/download.aspx