At the command line try examples:

yelp man:printf
yelp 'man:printf(3)'

or use

yelp man:printf & 

to carry on working at the command line. For a more permanent solution try adding

man () { yelp "man:$@"; }

to the last line of your .bashrc file. Then at the command line try examples:

man printf
man printf &

for the yelp viewer to come up. I like having the scroll-able window next to my CLI to alt-tab to.

KDE Helpcenter

KDE Menu > Applications > Help > Unix manual pages

Quick launch

By the khelpcenter help

:~$ khelpcenter --help
Usage: khelpcenter [Qt-options] [KDE-options] [url] 

The KDE Help Center

Generic options:
  --help                    Show help about options
  --help-qt                 Show Qt specific options
  --help-kde                Show KDE specific options
  --help-all                Show all options
  --author                  Show author information
  -v, --version             Show version information
  --license                 Show license information
  --                        End of options

Arguments:
  url                       URL to display

Command: khelpcenter man:apt will show the apt man page via the KDE help center.

With the quick launcher /1/ Mangonel:

The Mangonel is available from the Ubuntu repositories: http://packages.ubuntu.com/search?keywords=mangonel&searchon=names&suite=all&section=all

KDE kio-man

KDE Help center > Kioslaves > man

Using the man ioslave you are able to read the man pages installed on your system. It is easy to use...

As with any other KDE ioslave, it is possible to enter a URL, like man:/socket in any KDE application.

With the Konqueror - "man:apt"

Other browsers - The KDE System Settings > File Assosiations > html.

How good or bad the parsing of the kio-man html output is depending the picked browser.

The browser can be launched from the KRunner /1/.

The Kubuntu Forums has a topic: 'Graphical man page viewer' /2/ in the How To's section.

Links

1. KDE Launchers: http://www.kubuntuforums.net/showthread.php?59851-KDE-Application-Launchers
2. http://www.kubuntuforums.net/showthread.php?62631-Graphical-man-page-viewer

Gman

From the Ubuntu man page, Gman is a "GTK+ based front-end for man, a good replacement for xman."

Gman provides an index of the man pages installed on your local system and offers several options for viewing the man pages. The default option is to have gman open the man pages within an xterm session. This can be modified to suit your taste with four other options.

The other viewing options available are:

• ghostview
• Evince
• LocalBrowse
• NetBrowse

In order to change the application used for viewing, select View from the menu and then select the radio button next to your preferred application, as shown below:

The last two options require having the man2html package installed on your system and will bring up the man pages in your default browser.

In KDE we can search and display Unix manpages from the KDE Help Center or we can open and display the content of any locally stored manpage with Ark.

According to the Debian FHS user program manpages are .gz compressed and stored in /usr/share/man/man1 or /usr/local/share/man/man1, but there are more manpages stored in various subdirectories of /usr/share/man, named after the corresponding application name. This should also include manpages from installed applications not available through the Ubuntu repositories (e.g. installed manually or through a ppa).

In GNOME we may browse to the corresponding /usr/share/man subdirectory to open the manpage with file-roller and gedit.

By performing a custom search on Manpages Ubuntu only manpages of applications available from the official repositories will be found.

To edit manpages also see:

• How to create a manpage?

If you are willing to use your browser, you can visit The Ubuntu Manpage Repository. Here's a quote from that page:

Welcome to the Ubuntu Manpage Repository This site contains hundreds of thousands of dynamically generated manuals, extracted from every package of every supported version of Ubuntu, and updated on a daily basis. Traditionally, manpages are browsed on the command line. This project renders all such manuals included in Ubuntu into an HTML, web-browsable format.

In Kubuntu via Krunner (Alt+F2) type #ls or any other command. Just add a '#' in front.

see also: http://userbase.kde.org/Plasma/Krunner#Issue_.28shell.29_commands

I find GTKMan very promising.

Here a screenshot of it in action:

I liked Justin Solm's answer in that he added a line to his .bashrc to replace the man command with his gui man of choice, yelp. That is what I wanted, however sometimes I am running w/o X (such as through SSH). I wanted it to automatically fall back to the commandline.

At another post I found answers about how to do that, mostly those were checking the DISPLAY variable. That is good but one answer included a C program called RunningX that actually checked to ensure the DISPLAY variable is actually valid rather than just defined and non-empty. Even better! I recommend going over there and getting it!

Here is what I ended up with:

man () {
    if RunningX
    then
        yelp "man:$@";
    else
        /usr/bin/man "$@";
    fi
}

I'm sure this could be adapted for use with Gman, KDE's help center or whatever man viewer one prefers. It could be adapted for other uses besides manpage browsing as well.

You might want to try xdg-open which fires up the desktop environment's native help tool (yelp for GNOME, khelpcenter for KDE,...):

xdg-open man:printf

So out of all this answer I usually use this way, when I need to refer any manual.

man ls>/tmp/ls.txt && gedit /tmp/ls.txt

instead of gedit use any text editor.