If you want to create a document that contains checkbox images rather than “True” or “False” values, you can do so in two different ways.

Display Checkboxes With The Checkbox Merge Field Attribute

The easiest way is to add the "checkbox" merge field attribute to any boolean field that you want to display as a checked or unchecked checkbox. If your merge field looked like this:

{{!Opportunity.Checkbox__c}}

You can display it as a checkbox image by adding the attribute to the end like so:

{{!Opportunity.Checkbox__c checkbox="true"}}

Learn more about merge field attributes here.

Display Checkboxes With CSS

Checkboxes can also be displayed using CSS styling similar to the following example:

Display Checkboxes With Formula Fields

You can also display checkboxes by leveraging a formula field.

By adding the following formula field to your object, you can easily leverage it to place checkbox images into your S-Docs. (You do not need to add the field to the page layout.)

Note: Your formula field should have a Formula Return Type of Text and should be referenced as rich-text when merging into a template. The field used in the example, IsAccount__c, should be a checkbox field on your object that is checked by default.