The foundation, a conservation charity, set up the agency last year and receives all of its profits.
It initially focused solely on street fundraising. Simon Chuter, training and account manager for AAP, said it had decided to start door-to-door fundraising because of demand.
"A number of charitable organisations have expressed interest in door-to-door fundraising. Many of them have found that this approach can secure longer-term donations from older people," said Chuter.
AAP, which employs more than 80 permanent staff, has recruited four specialist managers to launch its door-to-door fundraising offering.
Caroline Langford, supporter acquisition manager for Plan UK, said: "Our experience shows doorstep fundraising is a really cost-effective way to recruit new long-term supporters for plan. We’re looking forward to working with AAP."