I hope you're having a great week so far. After trying this in my test account, I've discovered that there isn't a way to have this information at the bottom of your invoice. However, there are a few alternatives that may work with your specific request.
Using the "Message on Invoice" feature
This feature will allow you to type any information that's needed to go on the invoice. Here's how to locate it:
Go to the Sales tab in the left-hand menu.
Select the Invoices section.
Pick the Invoice you'd like to make changes to or press New Invoice.
Type in any additional details that you'd like to include in the "Message on invoice" box.
Once you're finished, click Save and Close, Save and New, or Save and Send.
Use Custom Form Styles
This option will allow you to customize any form style you'd like within your account. Below are instructions on how to use the feature.
Go to the Gear icon in the top right-hand corner.
Under "Your Company," pick Custom Form Style.
Select New Style and choose a form you'd like to customize.
Make any changes and when finished, click Done.
Let me know if this helps you out. I want to make sure your concerns are addressed. Enjoy the rest of your week!