Conga Composer can create a protected Word document, where the document is locked and cannot be edited after merging. However, you can use the TEXTBOX merge field to specify text that can be edited.
TEXTBOX
Syntax
{{TEXTBOX:FieldName}}
Notes
Conga Composer produces an editable Word Text Input box in the output file. Any merge fields that do not include this prefix will be populated with data, but not editable in the output file.
To use this feature, you must have a Conga Composer button that contains the WPD parameter value: &WPD=1.
If the TEXTBOX merge field is inside of a Word text box the field is not editable.
Usage
Include the &WPD=1 parameter in your Composer button URL so that the document that is merged from that button cannot be edited: