Security should not be a concern with using Google Docs platform. You can restrict the access of any template or your google drive folder where templates are being stored, see this article for more detail.

You can view our privacy policy for A5 Documents on app website or in KB, you can see this article. 

In addition, here are some other helpful articles on Google security:

Google Cloud Platform Security compliance:

Link to FAQ document regarding Google Security: You can find related question and go to drop down for more information.

Google’s Statement on G Suite security and trust:
“Google started in the cloud and runs on the cloud, so it’s no surprise that we fully understand the security implications of powering your business in the cloud. Because Google and our enterprise services run on the same infrastructure, your organization will benefit from the protections we’ve built and use everyday. Our robust global infrastructure, along with dedicated security professionals and our drive to innovate, enables Google to stay ahead of the curve and offer a highly secure, reliable, and compliant environment.”

Embedded privacy controls
Google made it easier to jump to key settings directly from the policy, helping you make choices about your privacy.
The revised policy is available here and was last updated in January 2019. 
Improving your privacy controls
Within the past year, Google updated My Activity so that you can better access and manage the data in your Google Account. We also launched a redesigned Dashboard, which allows you to easily see an overview of products you’re using and your data associated with them.
In May 2018, Google updated their Privacy Checkup with new illustrations and examples to help you make more informed choices about your key privacy controls. And since we understand that your preferences may change over time, the new Privacy Checkup enables you to sign up for regular reminders to check your privacy settings.
To learn more about these and other controls to manage your privacy, visit your Google Account.