I'm just starting to play around with RLM and RLD coming from a background primarily in building websites with ASP.NET Master Pages, where a single master held the layout for the site and the individual "pages" are really just content sections that appear in designated places on the layout of their associated master page. This means that if you want to change the commo header and menu used on all your pages, for instance, you change it on the master page that all the content pages use, and it's immediately changed for the whole site.

I'm trying to figure out if there's a way I can do that in RLM and/or RLD, have the basic layout common to all pages exist in just one document so it can be changed for all pages at once, and be able to create new pages that already inherit all of that outer page layout. Is there anything like that with RLM/RLD?

Not that I'm aware of. Not in RLM for sure, not sure on RSD as I haven't ventured into that one much, but I'm not aware of it having that feature either.

Right now your only recourse to creating repeatable building blocks is to create a master page of sorts that includes all the elements in place that you want repeatable and leaving the areas open that you want changable (typically this is the center area of your site that you add your content to). Make sure this is as complete as you can get it. Make sure all the classes and ID's are exactly the same for all of the elements invloved in the repeatable areas.

Now just duplicate that page to create the new pages.

From here any time you change anything in these areas it will change it in all the pages at the same time (exceptions would be things like column spans which aren't transferrable from one column to another other than copy/pasting them). As long as you maintain the same classes and ID's then anything you change, including colors, images, sizes, etc. will reflect on all the pages that share that same setup. Just keep in mind that if you do change something like a column's span within that area, you'll need to alter that separately on each page, but the rest will still be intact.

For example I tend to create the Header areas with Logos, Textual tag lines, Menu etc.; any sidebars that will be included in all or even just some pages; footer area; any sub areas that will be built around.

Hope that helps, it's quite a time saver to do that really, and does reflect to extend once you've exported it as well if you change any of the class or ID settings in the CSS it will do the same for all pages.