My Adobe XI has stopped converting PDF's to reduced sized PDF. I have updated the software but still not working. I am working on Windows 10. Any suggestions would be greatly appreciated.

I use Adobe XI Pro to reduce PDF sizes.  I generally open the PDF and then click on 'save as' and choose the reduced size PDF which reduces the PDF size.  The past few days no PDF documents are reducing.  It just comes up with the same size file.  I have checked and updated the software but I still have the problem.

Any suggestions would be greatly appreciated.