In MS office 2007 and above you can save your office documents as pdf. You will find this option in "Save As" menu option. Some time PDF plug in is not installed in that case you have to download plug in from here.
Instructions To install save as PDF plug-in:
Download the file by clicking the Download and saving the file to your hard disk.
Double-click the SaveAsPDFandXPS.exe program file on your hard disk to start the Setup program.
Follow the instructions on the screen to complete the installation.
How to use PDF save as plug-in:
After you install this download open the document you want to publish and then, depending on the program you are using, select Save or Publish to PDF or XPS from the Office or File menu.
For more information, search Office Help for "Save a file in PDF format" or "Save a file in XPS format".
To remove this Save as PDF plug-In
To remove the download file, delete the file SaveAsPDFandXPS.exe.
On the Start menu, point to Settings and then click Control Panel.
Double-click Add/Remove Programs.
In the list of currently installed programs, select Microsoft Save as PDF or XPS Add-in for 2007 Microsoft Office programs and then click Remove or Add/Remove. If a dialog box appears, follow the instructions to remove the program.
Click Yes or OK to confirm that you want to remove the program.