OK, this is possible, but there are limits.
The important thing to understand is that unless you configure it otherwise, the plugin will only show a record edit form if the user opens it with the private link with the “pid” code. Once they do that they can move from page to page within the multipage form because they will have a “session” that keeps the form for their record available. As long as the session is valid, they can jump in to any page in the form and make edits. This means that a link to a page within the form is the same as what you see in the location bar when you’re on a particular page in the form.
They can go anywhere (even off the site) and come back to the form…unless they go to the “thanks” page (page with the [pdb_signup_thanks] shortcode). When they go there, the session will be destroyed because it’s assumed they are done. The session will also expire on it’s own after a while, I think 24 hours.
Once the session is no longer active, they will need to use a link with the “pid” code to open the form again. It is possible to go to directly to any page in the form, and as long as the pid code is in the URL, the form will open.
That said, in a situation such as you describe, you may want to use a setup where the user is actually logged in (as a WordPress user) and then, with some custom code, the form pages would be available to them as long as they are logged in. This does require some coding to get working.
On the “previous” button, you’ll probably need to use a custom template to get that done, and add a regular browser “back” button, such as this:
<input type="button" value="previous page" onclick="history.back(-1)" />
