Newton-based photo- and video-digitizing startup EverPresent opened a second office last month in Watertown and the company plans to grow its headcount, said co-founder and CEO Eric Niloff. The new 2,500-square-foot Watertown location at 200 Dexter Ave. opened on June 23 and there are about 30 photo and video technicians currently working out of the space, Niloff said. "Adding a new location is stressful, but it's the best problem to have," he said in an interview. "We've been growing really…