Thanks for taking interest in GroupDocs.Viewer API.
Currently, the postscript format is not supported by GroupDocs.Viewer for .NET API. However, I am logging your request in our internal Issue Tracking System. The product team will further do their analysis to check if they could provide its support in the future. Furthermore, please note that the priority of any new feature increases with the number of requests from the users.
For the query related to GroupDocs.Conversion API, please create a new post on GroupDocs.Conversion Support Forum
where support representative will provide you required information.
In case of any confusion, please feel free to let us know.