Thank you for your quick reply.
I did not express myself clearly. I'm logged in as a super admin in the front end. How can I change the permissions for a document I have uploaded here?
I only want to associate this document with specific user groups. I found the normal form. In this form I can associate one user group. But in back end it is possible to associate more than one user group.
I am understand your idea, at frontend, we don't allow user to have much power to setup access levels for document as in the Backend side. You can open file: root -> administrator -> components -> com_edocman -> view -> document -> tmpl -> default.php and check line: 234 to 265, that code part is used to show the Access level fields when you add/edit document at Backend side. You will also need to update JS code at bottom of that file too