So I started to look for something else. I tried Remository but it just didn't install (blanc screen).
Then I found jDownloads. Unbelievable what a program! Everything I had been missing in Docman is in here. I just looked at jDownloads for a couple of hours now but it's an amazing piece of software.
There are many many options for customizing. It saves files into subdirectories, it's very easy to upload a file, it has a good search plugin, it has a nice dropdown menu for easy navigation, the layout is customizable, it picks up files which were uploaded by a regular ftp-program.
I like it very much!