The number of jobs in metropolitan Washington reached 1.9 million by the end of 1985, a 12 percent increase since 1983 and the steepest two-year increase since records have been kept, according to a Greater Washington Research Center economic study.

The expansion added 200,000 jobs to the area, "greatly exceeding" the number of jobs added in any two-year period, said Philip M. Dearborn, who conducted the study for MarkeTrends.

Salaries also were on the rise, the study showed. The metropolitan area, where income is above the national average, had a 12 percent increase in real earnings, paralleling the number of new jobs. Adjusted for inflation, real income increased 7 percent.

However, whether this "boom" in the economy will continue is unclear, according to Dearborn. The growth of the area's economy is dependent on the national economy and the federal budget, he said. "And those factors will have a significant effect on . . . the future of the local economy ."

MarkeTrends, which has been conducting economic studies for 25 years, has found repeated evidence that the local economy is dependent upon the federal government. "The dependence has shifted," said Atlee E. Shidler, president of MarkeTrends, "but it hasn't disappeared."

Almost 174,000 of the new jobs were in suburbs, such as Fairfax and Montgomery counties, where most of the private companies are located. Eighty percent of the jobs were in the service, retailing and construction industries, "those industries most easily affected by federal spending," Dearborn added.

Only 3 percent of the new jobs in 1984-1985 came from federal payrolls.

Intercad Corp., the software publishing subsidiary of the Vienna-based ERC International, teamed up with an Oregon firm last week to market both companies' software packages as one integrated product.

Intercad's graphics software will be marketed nationwide with a page composition software package made by Context Corp. of Beaverton. The Context software, known as DOC, is installed in several thousand graphics workstations worldwide and is used to produce technical documents. Under the agreement, Intercad has marketing rights for the DOC package.

Intercad's software package, the Illustrator I series, is used by companies in the aerospace, computer, electronics and automotive industries to produce technical graphics.

"The union of the Intercad Illustrator I with the Context page compostion software will provide the companies with a large-scale art and text system," said Jack Aalseth, chairman and chief executive of ERC International.

Martin Marietta Corp. received an $83 million contract from the Air Force last week to produce parts of a targeting system that will improve the effectiveness of fighter aircraft. The contract is part of a larger Air Force project awarded to Martin Marietta in 1982 to develop a low-altitude navigation and targeting infrared system (Lantirn). The company will produce the Lantirn targeting pod system, one of a two-pod system to be attached to the fuselage of high-performance aircraft.

The Air Force estimates that Lantirn will "significantly" improve the combat effectiveness of its tactical fighter aircraft, especially in central Europe, where nights are up to 16 hours long. Lantirn uses an electro-optical sensor to detect targets and enables pilots to fly at night in a day-like condition.

Martin Marietta is to deliver 700 of the targeting and navigation pod sets for use on the F16C/D and the F15E aircraft and 29 sets of computerized test and maintenance equipment.

The John D. Lucas Printing Co. of Baltimore will acquire Interstate Printing Co. next month, subject to the approval of Interstate's stockholders.

Interstate provides printing services to the New York and New Jersey metropolitan areas, and JDL has operated in Baltimore for 150 years.