Distance Tool

measure icon

Call this from Edit > Tools > Measure and choose Distance Tool from the drop-down list.  A dialog box with three tabs appears; make choices in the Settings and Mark up panels, then draw a line over an object in the PDF whose distance you want to measure.

View tab
 

The Measurement shows:

In the Cursor Location area, the X and Y coordinates of the current cursor position are dynamically displayed relative to a start point of X=0,Y=0. No signs are considered.
 

Settings tab

Markup tab