I don't know of any free software but a less expensive option is Nitro PDF. I used that before I got a copy of Adobe Creator.
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You can also blow up the PDF on your screen to 400% so it's high resolution and select the area with a snap-shot tool which will copy it to memory, then paste it in a program like microsoft paint, zoom out so you can see it all on one screen. Do your marking. Save the file as a graphic image and then print it with Windows by right clicking on the file and choosing print to a PDF printer like Cute-PDF writer (free) and do it that way.
It's crude but it works and I frequently do that at work where we don't have PDF software.
Once it's installed, open a PDF. From the menu at right, choose "Comment". At the top of the window will now appear a row of icons containing a voice bubble, a felt-tip marker, text-editing tools, etc. At far right will be an icon depicting a circle, a square, and a triangle nested together. That one is your "Drawing Tools". That's where you get the things you want to put in your PDF. You can choose your own line width and line color as well.