Thousands of engineers, scientists, medical personnel and other shortage-category U.S. workers here are in line for pay raises that will be announced soon and be effective with the first pay period in October.

The increases are the result of an annual review the government makes (in the Washington area it takes place in May) to determine if U.S. offices are paying enough, compared with home-town industry, to attract and keep workers in certain hard-to-fill jobs.

Most of the special-rate workers are engineers and already are paid higher salaries than nonshortage category workers in the same pay grade. Differentials range from 5 percent to more than 20 percent.

This year the government, prodded by the Defense Department with substantial help from Office of Personnel Management Director Constance Horner, gave special raises to 42,000 stenographers, typists and data transcribers here in grades 2 through 7. The increases range from 2.6 percent to 23 percent, or between $612 and $2,792 a year.

Defense, the largest single employer here, requested the raises to make it more competitive with private companies that often pay clerical workers more and offer fringe benefits such as free parking.

OPM officials say that because the clerical pay raises went into effect just before the local May wage survey, they will make a new study to determine if they are due new raises. Defense and other agencies are pressing for another raise and would also like to see most of the special-rate workers get the January pay raise due rank-and-file white-collar workers. President Reagan has proposed a 2 percent increase, and Congress is working on a 3 percent rise.Rating the Experts

Within the next three months 250,000 Washington area federal workers must decide their pension future. Should they stick with the old civil service retirement system, an excellent plan that offers guaranteed benefits based on salary and service, or switch to a new private-sector retirement program that includes Social Security and a generous tax-deferred investment option?

So far less than 2 percent of the federal work force has signed up for the new pension plan. But, because of the complex decision, half a dozen private firms here are doing a booming business advising employes on their pension options. For fees ranging from $12 to $32 workers can get computer printouts showing their benefits under both plans. One firm offers private counseling, at $40 for a half hour.

Tomorrow at 1 p.m. on WNTR (1050) AM, Walton Francis of the Washington Consumer Checkbook will rate the pension experts and give advice for federal employes picking a retirement plan. Meetings

The Senior Executives Association will hold its Nov. 23-24 seminar on ethics and integrity at the Radisson Park Terrace Hotel. Speakers at the session include former representative Robert Bauman of Maryland, former White House counsel Lloyd Cutler, General Accounting Office's Roz Kleeman and Los Angeles Times Washington bureau chief Jack Nelson. For details call 535-4328.

The Northern Virginia chapter of Federally Employed Women will hold a resume-writing seminar at its Oct. 7 dinner meeting at the Fort Myer Officers Club. For details call Eileen Feeley at 262-2737.