When you ask:
a tool to upload lessons (pdf or doc) - optionnal
Do you mean you have doc and pdf lessons already and you want to upload them to the Moodle? Yes, use the "Link to a file or Web Site" option in editing a course.
However, you are asking questions that are fundamental to Moodle. If you are using XP, or Mac, download the Windows XAMPP or MAMP version of moodle and install it.This is a very straightforward operation in these environments. In Vista or Windows 7, Microsoft has taken the view you have no idea what you want so prevent you from doing anything. You have to turn off so much stuff to get to the point where you can install a Xampp, that you are better off going to this site and looking at these videos, then downloading and installing a standard version of Moodle. All you need remember is that you are not installing a Developer database, but a UTF-8 collation. Since I did this myself, I have not had one bit of trouble with the environment, even when I have deliberate killed my Moodle testing stuff out - very easy to replace a Moodle when I wreck it. I have also added MediaWiki, Mahara, WordPress, phpMyAdmin and a couple of other toys for testing, and if I wreck one, the others are not affected, but I would love to know enough PHP programming to develop a single login procedure for all these PHP Apps <sigh>.
The best thing you can do is to just play with it. Install it to a stand alone, or if you can, to a private web werver, then just use the Moodle Docs and these forums to find out what you can do, how you can do it. Once you get the hang of it, it becomes simple and straightforward, even intuitive - and if it is giving you grief on something, come here and ask.
Moodle is the best learning environment I have used, with includes WebCT, Blackboard and others. It has provided the least amount of drama, the most reliable amount of uptime, and at a very cost effective level. The best part is we have full control over every aspect of the program, so we can decide when we want to do things, not be adapting, or subjected, to someone else's whims. We, I mean the organization I work for, has been able to develop new tools for use inside the Moodle environment, which access one of the largest repositories of videos and learning objects of its type in the world, which makes some things easier. Considering we are going to a national curriculum, this has become a timely and seriously useful tool. Unfortunately, of no value to any who does not have access to our digital learning bank, so will not be part of any Moodle near you, but I seem to recall some discussions about France developing something similar anyway and with your resources it could easily become a world leader.
Don't believe me, try it for yourself.