We have an issue when trying to create a PDF with a large JSON. The process works fine with 8MB of data in the JSON, but when trying to create a PDF with 16MB of data it will fail with "WebMap_as_JSON is empty. Web map has invalid JSON. Failed to execute (Export Web Map)". The custom print service is on an ArcGIS Enterprise Server running 11.1. I looked through the posts and did not see anything that deals with data size when having issues with the Custom Print Service.