If there are no links to documents, there is no way of checking if they exist (besides the actual guessing, which can take forever...). On the wget note, I quote :

Basically it comes down to: if the webserver has dirlisting enabled and no index file, you can see the files in the directory. If those are accessible depends on several factors... (me on LWP)

and:

The restrictions that Beatnik mentioned apply here as well though. (jorg on wget)

Greetz
Beatnik
... Quidquid perl dictum sit, altum viditur.