reducing file size (LOCKED)

I am running Adobe ACROBAT PRO V. 10.1.16 on an iMac running on OSX 10.11.4 w 8 GB memory.  I have been using the software for years, but only on this computer for a few months, since I bought the hardware. I am now having trouble with reducing file size on the pdf's I create.

If I take an Office document, (Word or Power Point, for example) and save as a pd, it used to be consistently possible to reduce the file size either by:

1. Going to FILE>SAVE AS>REDUCED SIZE PDF or,

2. Going to FILE>SAVEAS>OPTIMIZED PDF.

Now neither of these works anymore. I can still go to those commands, and implement them, but the software just does nothing - nothing happens - no little bar telling me it is doing things like it used to, no new file created where it asked me to store it - NOTHING!

Any suggestions?

Would love to get this (for me) critical feature back again. Is it s function of the hardware? Something this software doesn't like about the OS?

Thanks,

Tony Blair