For some reason less (<456) and man-db conflict. man-db in turn is a requirement for yelp, which is a requirement for gnome-core which is a requirement for gnome. In other words, you currently have a choice between less or gnome.
More here: http://email@example.com/msg1117622.html
verahill@debianstd:~/tmp/poppler_build$ sudo apt-get install lessReading package lists... Done Building dependency tree Reading state information... Done The following packages will be REMOVED: gnome gnome-core gnome-user-guide man-db yelp The following NEW packages will be installed: less 0 upgraded, 1 newly installed, 5 to remove and 0 not upgraded. Need to get 0 B/135 kB of archives. After this operation, 29.4 MB disk space will be freed. Do you want to continue [Y/n]?