Build smart doc by creating a Microsoft Word Template for Dynamics 365 + Secured Signing Smart Tag
Step 1: Create a Microsoft Word Template in Microsoft Dynamics 365

Step 2: Add Secured Signing Smart Tag
Secured Signing SmartTag Guide
Add Secured Signing smart tag into above created word template on the proper place which you want to sign.
Smart tag firstname/lastname/email can be replaced by Word Template XML Mapping.
