YFM Equity Partners said it has supported a £10 million management buyout of the business, which has carved out a profitable niche in the market to provide secretarial services and the like for law and financial services firms.
The Yorkshire-based investment firm expects Intelligent Office to maintain rapid growth at a time when many law firms are considering out-sourcing work.
Lots have faced pressure on fees since the financial crisis triggered a long downturn and a related slump in transaction work.
Intelligent Office has grown revenues by 40 per cent in the past three years.
The company made £611,000 pre-tax profit on sales of £14m in the year to September.
The deal provides a lucrative endorsement of Ms McPherson's faith in the potential for a business that could take work such as document management off the hands of businesses like law firms, which need to maintain complex records.
Business process out-sourcing specialists like Intelligent Office can achieve scale economies by working for multiple clients.
A graduate of the former Glasgow College of Food Technology who moved into client services, Ms McPherson founded Intelligent Office in 2001 through a buy-in of the former Docuserve operation.
She had spent two years in New York as Vice President of Bowne Business Solutions, which worked for investment banking and legal firms.
YFM said it invested £5m in the deal. Other details of the transaction were not disclosed.
It is understood YFM took a significant minority stake in the business. Ms McPherson sold some of her shares.
She had around 40 per cent of the shares before the deal.
Ms McPherson, 50, has been succeeded as chairman by James Greenbury, current chairman of the Parcel2go online delivery firm . She remains on the board as a director of the company.
The MBO team was led by chief executive Rachel McCorry, who said: "In the past year, Intelligent Office has experienced a 100 per cent increase in enquiries from UK top 50 law firms."
Intelligent Office UK employs around 160 people in Scotland and 685 in the UK.
The business acquired a controlling stake in Alloa-based transcription service Lawscript in 2006.
Intelligent Office UK's clients include HBJ Gateley and Wragge & Co.