Hi Juraj Tomana,
Thank you for contacting Syncfusion support.
We have checked your query "How to add Custom ContextMenu on each document seperatly in DocumentContainer". We can add the Custom ContextMenuItems on each document based on your content by checking it Header. We have prepared sample to meet your requirement in which we have added the Custom ContextMenuItems on each document. Please download the same from the below location.
Sample :
DocumentContainer_Sample
If we misunderstood your requirement, please provide more information regarding the requirement. This would help us to proceed further.
Regards,
Subashini M.