I have a document in pdf format on Adobe Acrobat Reader 7.0 which I want to print out. When I do so, the left hand margin is too small. All I want to do is change the margins of the entire document so the left margin is increased by 1/2 inch and right margin is decreased by same.

I can't for the life of me see how to do this. Is it impossible w/o purchasing the full Adobe Acrobat program? Is there any way around this, since it's not worth it to me to shell out the money for Adobe Acrobat?

All I need is the ability to play with the margins so I can three-hole punch the left side of the pages w/o cutting into the text.

I take it that you only have Acrobat Reader? Well what you can do is print the file a little smaller. You just select "fit to paper" or edit the percentage of scaling. It should make it small enough to give you extra space all around. If you had the full Acrobat program, yes you can do all this and crop and all that.
Another solution is to download another pdf program (Adobe isnt the only one). You can go to some place like www.download.com and do a search for "pdf edit" and you'll find some free programs (some shareware too) for you to play with.

Thanks a lot for the advice. Downloaded "Nitro PDF" from the site you recommended and was able edit the margins.