It is not clear how the documents, which have been posted online and appear to be photocopies, ended up in Greenpeace’s possession.
Edelman's reaction this morning was: "We do not talk about the work we do for clients."
The collection relates to the agency’s proposals to its client TransCanada to get a pipeline built to carry 1.1 million barrels of crude oil per day from Alberta to Eastern Canada.
The five documents are:
1) Energy East Campaign Organisation: Promote, Respond, Pressure, dated 5 August 2014
2) Research Synthesis, undated
3) Grassroots Advocacy Vision Document, dated 15 May 2014
4) Digital Grassroots Advocacy Implementation Plan, dated 20 May 2014
5) Strategic Plan: Quebec, dated 20 May 2014
In the first document Edelman advocates the use of a three-track approach spanning positive messaging, rapid response to attacks and "work with third parties to pressure Energy East opponents".
Elaborating on the latter track, it says it is designed to "add layers of difficulty for our opponents, distracting them from their mission and causing them to redirect their resources".
The agency promises to prepare a research profile of key opposition groups, including their record of legal issues, corruption and unfair labour practices, by examining public records, traditional media sources and social media.
It goes on: "We will begin with the Council of Canadians. Other possibilities include Equiterre, the David Suzuki Foundation, Avaaz and Ecology Ottawa."
The leak comes at a highly-charged moment for the oil industry in North America as pressure groups fight against the approval of another pipeline TransCanada is proposing to build to transport oil from the tar sands in Alberta.
Called Keystone XL, this pipeline needs to cross US territory, which could be authorised by a vote in the US Senate today.
However, the Energy East pipeline is said by some to be TransCanada's "back-up option" should Keystone XL be derailed in the US.
The Edelman documents show the agency casting the process of securing the backing for Energy East as a drawn-out battle with environmental groups that has already been played out in the US.