There seems to be an error in Aspose v. 11.0.0.
DocumentInfo.CreationDate property always returns an exception “CreationDate value is empty” when trying to set the property. The exception appears even when inspecting the property before we try to set it. Se picture below (This does not happen to ModifiedDate property).
This happens at least when pressing button Ready for Approval in Travel invoice – both for the main travel invoice pdf, but also for the travel invoice attachment (originally a png).
By googling the problem I found this link, but no solution.
For the time being I comment out line 207.