Use Case: 
I would like to generate mutliple documents at once and using Process Builder and followed the steps of this article to trigger the flow but something is not working. What am I doing wrong?

Consulting Reply: 
-Mass generation of documents will not work with Process Builder because of Salesforce and Google Drive limitations so you need to enable the app Batch Mode feature. And when using Batch Mode, you will need to change Action Type to “Create Record” (and not “Apex: as instructed in standard Process Builder article) as you will be creating new Document Request records.
-If using Process Builder to send an email from document action, you can review this article.

-SALESFORCE EDITION NOTE: Mass generation of documents does not currently work for Developer edition Salesforce orgs so our batch feature not yet available in this type of org.