We would like to find out if there is an add on app that can add a password automatically to the pdf generated in Quickbooks?

Hello there, @VdPSAR.

Let me share the third-party app store link so you can find tools that can help you generate a protected file. Since the password-protect PDF generated in QuickBooks is not available, you can use a third-party app.

You can visit this link for the App Store: App Store.

Also, you can go to this forum for Intuit developers. You can ask for guidance about third-party hosting applications: Intuit Developer.

Finally, you can read this article about personalizing and adding specific information to your sales forms in QuickBooks Online: Customise invoices, quotes, and sales receipts in QuickBooks Online.

 Let me know if you have questions about customizing QuickBooks-generated forms. I'm always here to help. Have a great day.