Hi Pedro,
Thank you for your update.
We have modified the sample to meet with your requirement using mail merge fields instead of bookmarks. In the given template document “Donor Annual Statement.docx”, we have replaced the bookmark with merge fields, which act as a place holder during mail merge operation. Please find the modified sample from the following link and let us know if this helps you.
Modified sample link:
https://www.syncfusion.com/downloads/support/forum/120706/ze/ModifiedSample-1718543447.zip
Please let us know if you have any concern.
Regards,
Sarath