Adding an attribute that doesn't change quantity available or stock?

It sounds like you want to set stock control at product level:
Admin page > Products > Product page > Product Data section > Inventory tab:
“Enable stock management at product level” = checked.

The alternative is to manage stock at variation level, which you don’t want.

I don’t want to set it at the product level since I will have varying stock on print sizes. So I want to set the stock at size.

However, the way WooCommerce works is by creating variations as a combination attributes. In this case Size and Framing.

Got it. If you want to do that using only the core plugin, you would have to setup two products, one for each size, with the frame as a variation, and then manage stock at product level.

If you don’t want to do that, check out:
https://www.woothemes.com/products/product-add-ons/
You will have one product with two variations. Manage stock at variation level. Each variation will have a “frame” add-on. The frames can have price which is added to the variation. I’ve not tried this extension so check that it meets your purpose before purchase. Woo have a pre-sales enquiry form if you need to check any points.

I’m not aware of any free plugins, though that doesn’t mean there aren’t any.

I’ve looked into the product add-ons plugin but definitely had some questions.

The main one being can I have an add-on change based on the attribute of size.

WooCommerce was a photography sales plugin in development that was supposed to be released in September but who knows what exactly it will do or when it will launch.

Best to ask Woo for an authoritative answer:
https://www.woothemes.com/contact-us/#sales-form

Hi, mattmikulla. If it’s not too much trouble, would you mind sharing how you ended up solving this problem?

@toddjob

I never figured it out and put the issue on the back burner.

Here’s a couple more add-on plugins you could look at:
https://codecanyon.net/item/woocommerce-extra-product-options/7908619
https://codecanyon.net/item/product-options-for-woocommerce-wp-plugin/7973927