Where can I buy the soccer video doccumentary entitled "This is Pelé" (original
portuguese title: "Isto é Pelé")?

I was unable to find a location where you could purchase this video. However, 
you can rent a copy of this video through the Brazilian-American Cultural 
Institute (BACI) in Washington, DC. In order to rent you will need to become a 
member of the organization. Annual membership is $20. As a member you can rent 
the video from their library for $10 a week with one-way postage and handling 
included. Local residents can rent video's for $3 each per day. 

The BACI website: http://www.bacidc.org/

You can find information on the "This is Pele" video under: Home > Video > 
Documentaries > 52 This is Pele. 
http://www.bacidc.org/documentários.htm

I was able to find a website that sells soccer videos, which may be of interest 
to you. This site (www.lacancha.com) also carries a diferent Pele video 
called "Pele - The Master and His Method." It is available for purchase for 
$34.95. 
http://www.lacancha.com/Soccer_V114.html

Well, thanks for trying.

You might want to try the companies that produced the video:

Luiz Carlos Barreto Produções Cinematográficas Ltd. and
Rede Globo de Televisão

(http://us.imdb.com/Companies?0188004)

I found that you can contact Barreto at:

L.C.Barreto/ Filmes do Equador
Av. Franklin Roosevelt, 194 - sala 908
20021-120 Rio de Janeiro RJ 
tel (21) 2533-2128 fax (21) 2262-3049
lcbarreto@uol.com.br 

(http://www.kinoforum.org/guia/2002/index.html?
http://www.kinoforum.org/guia/2002/guiaf_contatos.php?tipo=prod)

and Rede Globo has a web site:

http://redeglobo.globo.com/