Based on our experience with 5.7, there is no feature that allows you to push changed default content to existing pages.

The online guide located here, suggests this is available, but to our knowledge it is not (yet perhaps):
https://www.concrete5.org/documentation/using-concrete5-7/dashboard/...

You can, of course, make default content available to new pages. You will have to walk through the process to become comfortable with how it works. When adding default content to a page type (Go to Dashboard, select Pages & Themes, select Page Types, then click the Output button (for the desired Page Type), then click the Edit Defaults button), a new page will open in a separate tab, so it's a bit confusing at first. Turn on edit mode, make your changes, then save and return to the dashboard and return to your website and you should see your default content appear in the page the next time you select the page type for a new page.

Hope this helps!

Thanks. I was following this guide, and was able to update the content, but it only appears when I create NEW pages with that template. I'm trying to push the updated content to existing pages that are using that template. On the page you referenced it has this text:
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Set up on Child Pages
This option allows us to "push" content from the default page type template defaults to every page on the site that currently uses that page type and template.
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But I don't see this option anywhere.

Sorry for the confusion...I updated my post to provide clearer details.

You are correct, this feature in the documentation is not currently an available feature, unless its hidden somewhere and someone discerns how to get to it.

Okay. Not the answer I was hoping for, but at least I can quit looking for it. Thanks.

Excellent! That did the trick. That page on Online Guide could use some clarification.

Hello everyone, I understand if we create/modify a block , we can left-click on the block and "Setup on child page".

But what about if we remove a block? Is it possible to push the "remove" update to existing pages?

You can remove a block from childpages the same way as descrobed above. Choose 'setup on child-pages and uncheck the pages you would like the block removed from.