How to edit page permalink structure, if used custom WP directory

I’m not sure I’ve understood your problem.

Here‘s about permalinks.

And if you want your root to be site.com you should extract the WP archive (the downloaded .zip file containing WP) out of it’s folder (wordpress.zip/wordpress/all the files), archive it (wordpress.zip/all the files),upload it to server and then extract it and run the install.

Then read the permalinks tutorial and set it however you’d like.

Main problem – how to add extraparameter to page permalink? so not site.com/page.html but site.com/fld/page.html. But it should be page. not post

You define your WP directory in Settings->General
wp-admin/options-general.php

The address should contain site.com/fld

But for the part with page.html I’m not sure. I use in permalinks /%postname%/.html and I have site.com/post.html and site.com/page . So no page.html

Regardless if you want page or post, if you want the adress to contain the actual WP installation you set it up on Settings->General

But again, I’m not sure I fully understand your problem.

Ok. Forget about other dir etc. How can i add folder parameter to page url. e.g. if i use permalink mask /fld/%postname%, page wil still have site.com/page-name url, no /fld/.it will apears in posts only.

I don’t know if it’s possible that a WP installation contains different urls (as your case) for pages and posts. Could be that I’m wrong.

There’s a similar issue here.