Moving to Lightning - Here are some helpful notes

We recommend reviewing the following articles:

Lightning Component:
Help Content - Add the DocGen Lightning component to page layouts

Lightning Experience DocGen Package Designer:
Help Content - Lightning Experience DocGen Package Designer

Create a button to generate documents in Salesforce Lightning:
Help Content - Create a button to generate documents

Creating Mass Button in Lightning:
Create Mass Button in Lightning

Information on being able to save your output items as Files:
Help Content - Store attachments to Salesforce files