Can no longer measure PDFs

Looking for help. 

I often need to measure PDFs in Acrobat.  I have a Macbook Pro that is operating on Senoma 14.6.1.  I am unable to measure a PDF.  Acrobat is open, PDF has just been created and I navigate to Measure Object and then to the Measuring tool.  I click on my starting point and hold shift for a straight line and EVERY TIME the beachball of doom comes up and the programme freezes.  I then have to force quit.  Just to note, it also happens if I don't hold shift.

Any ideas?