This excerpt taken from the PRGS DEF 14A filed Apr 10, 2009.
What is householding of proxy materials?
In some cases, shareholders holding their shares in a brokerage or bank account who share the same surname and address and have not given contrary instructions received only one copy of the proxy materials. This practice is designed to reduce duplicate mailings and save printing and postage costs. If you would like to have a separate copy of our annual report and/or proxy statement mailed to you or to receive separate copies of future mailings, please submit your request to the address or phone number that appears on your proxy card. We will deliver such additional copies promptly upon receipt of such request.
In other cases, shareholders receiving multiple copies at the same address may wish to receive only one. If you now receive more than one copy, and would like to receive only one copy, please submit your request to the address or phone number that appears on your proxy card.