batch change exposure by delta

 Dont know how to do what?

This idea of a delta is counter productive. 

First, you don't really know your raws at least, are over or under exposed via LR. It doesn't provide that data. You need to view a raw Histogram via something like RawDigger to nail actual exposure. 

Next, any rendering in LR can appear 'over exposed' or 'under exposed' when the source data may not be because of the current rendering settings. Below is a good primer about this from Jeff Schewe to look over. 

If you calibrate the display to actually match a print, they match and the print doesn't look 'too dark' compared to the print. 

See:

Per is right that you shouldn't do this. You should calibrate your screen correctly and view your prints using good lighting. That said, if you select multiple images and hit the + or - in quick develop, it should apply to all selected images as a relative adjustment as long as you are in grid view

If your prints are too dark, your screen is too bright.

Reduce the brightness of your screen to match the prints, or even better, calibrate your monitor with a hardware calibrator, with brightness set to 100 - 120 candela. This will also create a custom monitor profile, which describes your monitor accurately. With an accurate monitor profile, Lightroom will display your images accurately. Then use the correct printing profile for your printer/paper combination, and the prints should be quite close to what you see on screen.