The buyout, valued at £13m, is being led by a management team fronted by Chris Spratling, who said the group was "delighted" to have completed the deal and secured the future of the business.
He said: "We are now fully funded and debt free and can now focus on bringing our customers all the services and products that they have such huge affection for.
"There are tremendous opportunities for our businesses in financial services, books and healthcare and significant plans to expand all aspects of the Reader's Digest business in the UK."
More than 130 jobs were put on the line after the UK arm of Reader's Digest filed for administration with Moore Stephens in February.
The UK subsidiary fell to the administrators after a deal to help bail out the company's £125m pension deficit fell through, an issue that the Reader's Digest Association (RDA) blamed on the UK Pensions Regulator.
The business had previously reached an agreement with the trustees of the fund to pay £10.9m in cash and one third of its shares to fill the deficit and transfer the scheme to the Pensions Protection Fund. However, this deal was rejected by the UK Pensions Regulator.
Speaking at the time, Mary Berner, president and chief executive of the American parent company Reader's Digest Association, said: "The pension problem in the UK was unique and of longstanding origin, going back many years."
According to Better Capital, Reader's Digest Association has agreed to allow the UK operation to publish under the Reader's Digest brand through a licence agreement.
Reader's Digest UK bought out of administration
Reader's Digest UK has been bought out of administration by private equity group Better Capital in a deal that has saved 135 jobs at the UK subsidiary.