can i download a PDF reader

1. Adobe Acrobat Reader
Adobe Acrobat Reader for viewing and printing Adobe Portable Document Format (PDF) files.

    * To install Adobe Reader
    sudo apt-get install acroread

    * To install Acrobat Reader Plugin for Firefox
    sudo apt-get install mozilla-acroread acroread-plugins

2. XPDF
xpdf is a suite of tools for Portable Document Format (PDF) files. This tools include a PDF viewer and PDF converters (including to/from PostScript).

    * To install this tool
    sudo apt-get install xpdf

3. PDF Viewer for Gnome
Evince is a simple multi-page document viewer. It can display and print PostScript (PS), Encapsulated PostScript (EPS), DJVU, DVI and Portable Document Format (PDF) files. When supported by the document, it also allows searching for text, copying text to the clipboard, hypertext navigation, and table-of-contents bookmarks.

    * To install this tool
    sudo apt-get install evince

4. PDF Viewer for KDE
Kpdf allows you to view PDF (Portable Document Format) files. This package includes kpdfpart so you can embed in konqueror or run as a standalone application. This package is part of KDE, as a component of the KDE graphics module.

    * To install this tool
    sudo apt-get install kpdf

5. PostScript Viewer
gv is a comfortable viewer of PostScript and PDF files
for the X Window System. It uses the ghostscript PostScript interpreter and is based on the classic X front-end for gs, ghostview, which it has replaced now.

    * To install this tool
    sudo apt-get install gv

More information can be found here: http://vntutor.blogspot.com/2008/01/top-5-pdf-readers-for-ubuntu-linux.html

Ubuntu comes with a PDF reader pre-installed. The program is actually called evince but Ubuntu gives it the friendlier name Document Viewer. You can search for either name in the Software Centre to check that it's installed. It should open automatically if you double click on a PDF file in the file manager or try to open one from your web browser.

It isn't automatically placed in the Applications menu though. If you do want it there, go to:
System > Preferences > Main Menu
to open the menu editor. In the left pane, click on Graphics, then tick the box next to Document Viewer in the right-hand pane.

Seems you are new to Ubuntu...: read the Ubuntu Manual, it's very informative: http://ubuntu-manual.org/
Click on the "download Button" to download the latest PDF version.