Problems with the installation

I have a problem on a PC that has 2 types of profile set: Administrator (who is authorized to install sw) and User (who cannot install but can use sw).

If I install Librecad using the Administrator profile, the User who must use it does not see it: how can I solve it?

You log onto user profile and launch installation process who will request for Administrator password.

I have installed the sw from the administrator profile. It is the User who does not see Librecad installed.

Yes, that's why @fa201 advised to use the user account and not the administrator account to run the installer.
The installer will ask for admin permissions. You have to grant them, either by simply accepting, when the user is in the Administrators group or you will be asked for username and password for a valid administrator account.
Then the user should be able to run LibreCAD without admin privileges.

ok ... does this mean that if I have 3 user profiles (in addition to the administrator one) I have to repeat the installation 3 times?

No, in this case move the shortcuts from users start menu and/or desktop to the public all user location.
The application can be installed only once and when you want to share it between users you have to use shortcuts in a common place or create individual ones for each user who will use it.

LordOfBikes wrote

in this case move the shortcuts from users start menu and/or desktop to the public all user location.

Could you tell me how it's done?