Edit Pages Templates is greyed out

Hello jameskrieg,

You can edit a page template using the steps below:

When you edit a page template, any changes you make are applied to all pages that use that page template.

1. Click  in the toolbar, then choose Edit Page Templates.

2. Select the page template you want to edit in the sidebar on the left.

3. Do any of the following:

• Modify existing design elements: Select any design elements on the page, then delete them, or edit them using any available formatting controls in the Format  sidebar. To learn how to change the background of a page template, see Change the page background.

• Add images: To add a placeholder image, click  in the toolbar, then choose an image. Images you add to a page template become placeholders. An image you add to a placeholder in your document has the same size and placement on the page.

• Add text boxes: To add a placeholder text box, click  in the toolbar, then use the controls in the Format  sidebar to style it: add a border, choose a size and font for the text, and so on. Any text you type in the text box in your document has the same style you applied to the placeholder text box.

• Set how headers and footers appear on the page: Click the page template in the sidebar on the left (so nothing is selected on the page). In the Format  sidebar, select the “Show header and footer” checkbox to show headers and footers on pages that use this page template. If you don’t want the headers and footers to match the ones on the previous page in the document, deselect the “Match previous page” checkbox. (If you don’t see these controls, or the top of the sidebar doesn’t say Page Template Layout, make sure nothing is selected on the page.)

If you can’t select the header and footer checkboxes, turn them on for the document in the Document  sidebar.

4. When you’re finished, click Done at the bottom of the window.

You can also find those steps in this resource: Create and use page templates in Pages on Mac - Apple Support

Should you still be unable to edit a page template, you'll want to reach out to Apple Support so they can look into this further: Contact - Official Apple Support

Take care.