Full Error Message:
“Error while creating new document. Error message: Connection reset”

-You may see this error message when trying to generate a document and there is an issue with Salesforce doing performance degradation, service disruption, or maintenance in your server instance: https://status.salesforce.com/.
-Look for your server instance from this status report and see if there is any reported disruption from Salesforce. You can click on your server instance for more information. If you’re not sure what you server instance is, you can find it by looking at URL in open Salesforce window, example “NA78.”

How to resolve: 
Wait a few hours to see if Salesforce has marked your server instance as “available” and then test document generation once again to see if error now resolved.