Hello,
Thanks for your post. I noticed that you were using Spire.Doc Free. In that case, when using different Spire products in one project, you need to use the corresponding dlls from
Spire.Office Free. If you have purchased one of our commercial product and want to use it together with another free one, I am sorry it's not available to do so.
Best regards,
Simon
E-iceblue support team