MLB.com's Jim Callis reported on Tuesday that Kramer agreed to an $850,000 signing bonus, which is $144,800 below the slot value assigned to the 62nd pick. Pittsburgh announced the signing on Wednesday.
The signing of Kramer, a shortstop out of UCLA, comes a day after the Bucs signed first-rounder Kevin Newman and only a few hours after they introduced Ke'Bryan Hayes, their compensatory first-round selection.
Ranked by MLBPipeline.com as the Draft's No. 165 prospect, Kramer sat out all of 2014 following shoulder surgery, received a medical redshirt, then hit .323/.423/.476 with seven home runs and 34 RBIs for UCLA this spring.
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The Pirates also signed three late-round selections, all right-handed pitchers, on Wednesday morning: 20th-round selection Tanner Anderson from Harvard, 21st-round pick Nicholas Economos from Mercer County Community College and 30th-round selection Mike Wallace out of Fairfield University.
After selecting Kramer, Pirates director of amateur scouting Joe DelliCarri said the Pirates' scouts saw "great signs of continuing strength" in his surgically repaired shoulder.
Some scouts believe Kramer will continue to play shortstop at the next level if he returns to full health. The sweet-swinging left-handed hitter could also stick as an offensive-minded second baseman given his advanced approach at the plate.
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.