Add shading to a PDF document

[kgn]

Within Adobe Acrobat X Pro they have a measuring tool, but besides it's measuring abilities it allows me to shade a room or area on a blue print. This allows me to print the document with rooms or areas of the document shaded in certain colors to represent specific things.

I'm looking for a free or cheaper software solution than Adobe Acrobat, which is $450. My trial for it is expired.

I'm hoping someone is out there that can help me. I've linked to an image that will show you what I'm trying to accomplish.

Thank you for your time and help with this problem, I truly appreciate it.

Image of what I'm trying to accomplish:
http://i50.tinypic.com/20po806.png

[RicheemxX]

Well there certainly are cheaper alternatives you can try Foxit and NitroPDF are two that come to mind. They both have free trials, so you can see if you can get a similar feature from either. I was looking at some of the free tools I have and none really seem to have that specific type of function.

[kgn]

Foxit Editor and Nitro both have this type of function, however its crude at best and you cannot use snap points to follow say the contour of a radius wall on a blue print.. and they don't offer transparent filling.