Three years after acquiring document technology company Litera and then investing $100 million into creating the portfolio company Litera Microsystems, the investment firm K1 Investment Management has sold the company to Hg Capital Trust Plc.

During its ownership, K1 says, Litera tripled its revenue to become one of the world’s leading providers of end-to-end document management software. Litera has some 1,300 customers, including some of the largest law firms and life sciences firms in the world.

In 2017, K1 announced that it was combining four leading document technology companies — Litera, Microsystems, XRef and The Sackett Group — into a single business, and that it had invested over $100 million of equity behind the combination.

Terms of the transaction announced today were not disclosed.

For Hg, Litera becomes the sixth legal and compliance business in its portfolio. Others include STP, a provider of insolvency and law practice software in Germany; Mitratech, a global provider of enterprise legal management (‘ELM’) software to corporate legal departments, based in Austin, Texas; and Citation, a U.K.-based provider of subscription-based compliance services.