Security contractor PAE said Tuesday that private-equity firm Platinum Equity has agreed to acquire it from owner Lindsay Goldberg, also a private-equity company. The acquisition marks the culmination of a period of significant growth for PAE. Last year, the company bought the global security and solutions business unit of U.S. Investigations Services, which specializes in litigation support, biometric capture, training and security consulting, as well as A-T Solutions, which provides counterterrorism services. Lindsay Goldberg originally acquired PAE in 2011 from...