How do you change tabs/indents to 0.17 inches on whole document

I am writing a novel, composed of dozens of documents. I wish to go through, document by document, and change my indents to 0.17 inches, to be consistent with my 12 point Garamond font.

 Someone posted this response for me, but, while I initially thought it worked when I did a quick test, it is no longer working for me:

Format -> Text -> Increase/Decrease Indents

 Decrease is now greyed out for some strange reason.

 Can someone please explain EXACTLY how to go through, page by page, and change the indents to be 0.17 inches, for a formatting newbie?  I don't want to do the whole novel in one go, because I want to monitor for formatting mistakes as I go.  I've got a ton of italics and other formatting, like scene breaks, that I wanted to make sure to preserve.  Many thanks.

Change the indent for a single selected paragraph, using the Format -> Text -> Tabs and Indents pane.

Make sure you can find the original sample text again if needed. The easiest way to do this might be to create a FormatTest document outside of your Binder.

Use the Format -> Text -> Copy/Paste Ruler commands to apply it to any other text you select.

Use the Project -> Text Preferences command to make the new ruler the default for new documents in this project. Scrivener -> Preferences -> Formatting to make it the Scrivener-wide default.