Hi Genie,
What program do you have? Acrobat or Adobe Reader?
If you have Acrobat you can use the TouchUp Text tool to make minor edits such as mispelled words, typos, etc. But if you want to do more editing than that, you should do it in the program the file originated from ( such as Word), then reconvert to PDF.
Hope this helps,
Dimitri
WindJack Solutions
www.pdfscripting.com
www.windjack.com