Fillable Document is a great add-on for Commercial, Educational as well as Non-Profit organizations for all your document automation needs.
Quota is applied per month and per person to the following
Document generation - how many documents (Google Doc, Slide, PDF etc) can be generated in a month
Responses - how many form responses can be saved in a month
Bulk document generation - how many documents can be generated in bulk from Fillable Document for Sheets in a month
Free vs Paid plans:
The Basic plan of "Fillable Document" is FREE with a limited quota.
The quota resets at the start of every month (when users try using Fillable Document).
For professional features and additional quota, you can take a paid plan.
Note: Single license works for both Fillable Document, Fillable Slide and Fillable Document for Sheets add-on.