The extra pages url's within our system are not automatically rewritten by the SEO addon. We created the extra page feature to allow clients to use the same system of page creation within a few extra "supporting" pages for their classifieds and auction sites. We have no idea how these pages will be used for in the final site so can't "propose" or "lock" a url to any of them. While we make use of a few extra pages for our default design we have no idea of their final purpose. We can only suggest tutorials on the Internet to create rewrite rules in the htaccess file. But for example if you wanted to rewrite the page of the default design we use as an example of a pricing structure to point to "pricing.html" you would use a rewrite rule like this within your .htaccess file:

RewriteRule ^pricing\.html$ index.php?a=28&b=143 [L]

Whenever someone used the link like:

http://www.yoursite.com/pricing.html

They would be redirected to the following url within the system (though they wouldn't see that in the address bar of their browser):

http://www.yoursite.com/index.php?a=28&b=143

Creating the rewrite does not rewrite the link within the default design. You would then need to search through all of the page templates or site text where the "http://www.yoursite.com/index.php?a=28&b=143" link url would be and replace it with "http://www.yoursite.com/pricing.html". You can do this in the admin at Design > Text Search.

What that last paragraph means is that if you changed the pricing extra page url to "http://www.yoursite.com/pricing.html" using a rewrite rule as described above adding that rule to the htaccess file does not automatically change all links within the html of the design to use that new url. With the specific case of the pricing page that is a default link within the header and footer of the default design. So you would need to go to the header.tpl and footer.tpl templates of your design and look for the "index.php?a=28&b=143" and replace that link with the rewritten link "pricing.html" within the html of those templates for that rewritten url to be "in use".