I'm sorry, I should've been clearer in my question. I wasn't asking what "flatten" means, I was asking what the actual problem we're trying to solve is. Are we talking about documents that reside in the Laserfiche repository and you want users to not be able to modify them there? Or are we talking about documents being exported out of Laserfiche and how to merge the annotations into the image when that happens.

For documents in the Laserfiche repository, that functionality is controlled by the Annotate right. If a user has See Annotations but not Annotate rights on an entry, they can see the existing annotations but not add, modify or delete them.

If we're talking about documents exported out of Laserfiche, then it would depend on your exported format. You can look at the SDK documentation for the DocumentExporter class in Laserfiche.DocumentServices.