Hi Mier,
Thank you for your interest in Syncfusion Products.
DocIO does not have a support for adding check box from the control tool box to the word document. DocIO can insert the check box to the word document similar to adding check box through MS Word. We have created a simple sample for your understanding. Please find the sample from the below link. Try running the sample and let us know if this helps you.
Sample:
Sample1765051749.zipFor more information regarding check box, please refer the below link.
http://help.syncfusion.com/ug_92/Reporting/DocIO/Windows%20Forms/default.htm?turl=Documents%2F441241checkbox.htmPlease let us know if you have any questions.
Regards,
Poornima