Two main programs used by companies all over the world is Adobe Acrobat and Microsoft Office. The two complement each other. But not all of us can afford to buy both, or psosibly even one. Fortunately, there are free alternatives that may not operate exactly the same, but quite similarly.
Microsoft Office - Free Alternative - OpenOffice
The most popular known - free - alternative to Microsoft Office is OpenOffice. It is owned by Oracle and is filled with good features you wouldn't expect for free. Follow the steps to download and install OpenOffice.
1) Go to: http://www.openoffice.org/
2) Click "I want to download OpenOffice.org".
3) Click the download link that appears underneath.
4) Install the program.
You can now create documents, presentations, draw, etc. It is quite nice, doesn't beat out Microsoft Office, but definitely great for being free.
Adobe Acrobat - Free Alternative - Oracle PDF Import Extension
NOTE: Requires OpenOffice beforehand
3) Once the file has downloaded, double-click it to install it in OpenOffice.
4) Start OpenOffice.
5) Click File > Open
6) Select the PDF file you wish to edit.
7) Begin editing.
NOTE: This does force you to download and install OpenOffice to be able to do this, but it's a decision of using what's free, or paying around $200.
NOTE 2: There are many alternatives to Microsoft Office. Here is a review of some free ones you can check out (but which likely can't edit PDFs): http://www.notebookreview.com/default.asp?newsID=5431&review=Free+Alternatives+to+Microsoft+Office