CDI Corp. (NYSE: CDI), an engineering and IT staffing firm headquartered in Philadelphia, acquired EdgeRock Technologies LLC, a privately held, specialist IT staffing firm headquartered in Boston.

In an asset purchase, CDI acquired 100% of EdgeRock members’ interests for approximately $31 million in cash, subject to standard working capital adjustments. CDI will pay up to an additional $4 million contingent on future operating performance.

EdgeRock targets the enterprise resource planning sector and the acquisition provides CDI with a national platform for specialist IT staffing and relationships with consultants to SAP, Oracle and PeopleSoft projects. EdgeRock’s practice also brings CDI other specialized IT skill sets, including business intelligence and data analytics.

“The acquisition of EdgeRock represents an important step in our expansion of CDI capabilities to more specialized areas of IT staffing,” said CDI CEO and President Scott Freidheim. “Working with EdgeRock, and leveraging their strong access to experienced talent in ERP and other specialized technology sectors, we can better meet growing demand from existing and new clients to realize greater value from their technology investments.”

EdgeRock will become a division of CDI and continue to operate under the EdgeRock Technology Partners brand name. The current EdgeRock leadership team will continue to manage the day-to-day operations of the business.

EdgeRock reported approximately $44 million in revenue for the 12 months ended Aug. 31. It was founded in 2005 and operates nationwide. In addition to its Boston headquarters, EdgeRock has offices in Tampa, Fla., and Phoenix.

CDI ranks No. 20 on Staffing Industry Analysts’ list of largest staffing firms in the US. It also ranks No. 6 on the list of largest US engineering staffing providers, and No. 18 on the list of largest US providers of IT staffing.