On average, how much weight does pasta pick up from water?
Google, “pasta absorbs weight water”.
http://www.professionalpasta.it/Dir_3/3_techno/3_dry_/chap_2_1.htm
I absolutely guarantee that this is more than you ever wanted to know about how much water pasta will absorb. 
Atually… No!
That site gives lots of information on how to remove water from pasta, and gives it in a very thourough, yet easy-to-follow way. They do specify that dry pasta has to have a moisture content of less than 12.5%, but they do not discuss the final cooking of the pasta.
This site claims that pasta has >50% water content, but doesn’t get into detail.
This site on the other hand gives a more specific value of 66%, but yet again without backing it up with any sources.
I don’t know the answer, but it’s certiainly easy to find out. Weigh some dry pasta. Boil it. Weigh the boiled pasta. The difference is the weight of the water.
And you can still eat the pasta! Answer the question and make a meal, all in one step.
Yes, but note first that so-called ‘dry’ pasta contains up to 12.5% water!
Didn’t you read DDGs link above?
But the OP asks how much water is absorbed. The quantity of water at the start of the experiment is irrelevant.
What you want is the change in water content.
But wouldn’t the amount of water absorbed change based on how much water is originally in the product?
I am asking as a portioning question for doing food for a fundraising function.
I guess the question could be asked this way:
If I wanted to provide 10 pounds of cooked pasta, how much dry pasta do I need to cook granted pasta is not real expensive but its for a fundraising event and we would like to get as much revenue as possible.
Food will be prepaid and preordered I just dont want to have 10 pounds of dry pasta left over. Especially since storage after the event is an issue and obvious excess materials would probably result in griping and accuations of intentionally buying extra to keep for myself (please spare me the psych analysis, I know ).
Well, the fundraising answer is this:
Raising money at fundraisers is a myth. In fact, most fundraisers don’t raise money in and of themselves - the primary source of gifts comes from acquainting a donor to the organization and cultivating that relationship over a longer period of time than that one fundraising encounter. The question therefore should not be “what is the minimum amount of pasta I need to make money?”, but “are we asking potential donors for gifts in the right manner with the best possible pasta available to our limited resources?”. Serving one plate of lasagna donated by Emeril to a wealthy donor who is ready to contribute a large gift will yield more gift money than 1,000 watered down spaghetti dishes served to random people pulled off the streets.
Of course, that’s probably not what you’re looking for, is it?