Good app free or low cost to draw floor plans

[Completetech]

I often have to draw out floor plans for doing wireless surveys or for running cable. I need to be able to add items or notes to "locations" of where items will be going. Such as LAN drops ect. I am hoping to be able to export or save the file as a PDF and hopefully options for email and or Dropbox.

Does anyone have any experience with anything similar to this. Any other contractors using anything to roughly accomplish what I am looking for.