Although we are most familiar with Adobe when dealing with PDF and PS files, Linux system has some of its own programs that handle these types of files.
The default PS and PDF viewer on the system is kghostview. If you used file manager and double click these files, then the PS and PDF viewer automatically starts and displays these files.
Another PDF viewer is xpdf, which is the default application to display pdf files (although you can change that easily). It has most functions of Adobe Reader, but the interface is not as good.
Another program that deals with PS files is ggv (Gnome Ghostview). It does have a small problem that, when accessing from terminal, it displays warning messaegs upon launching. No such error when using X-win32.
Finally, Adobe Reader is installed. The command name is acroread.
All these programs let you view, mark pages and print.
Here is how to open pdf file automatically
using acroread, either from file manager or from browser.
You can convert back and forth between postscript and pdf. The programs are called ps2pdf and pdf2ps. They do this by calling ghostscript. I think pdf2ps does not do a good job on Redhat system, but fortunately most of the times it is the other way around and ps2pdf works well.
for example to convert myfile.ps to a pdf file, you could
ps2pdf myfile.ps myfile.pdf
If all you have is a dvi file, you could first do
dvips -o myfile.ps myfile.dvi
to produce a postscript file. Then you could use the ps2pdf command above to produce a pdf file.
Of course, start with a Latex file you could simply use pdflatex to avoid all these troubles.
To handle DjVu files, use the DjVuLibre package. Type "man djvu" for more information. It has a viewer (djview), a browser plug-in, and command line tools like djvups (which converts divu documents into ps format: usage: djvups filename.djvu filename.ps).