Signed Document, PDF Contents show Expired!

Associates are opening PDF files on our network share.  PDF documents were signed.  When opened with Adobe XI or Reader DC, the file contents shows, "EXPIRED" in the document and the actual contents are not visable.  It was communicated that this happened in the past and as long as the associates used Adobe Acrobat Reader AND not Reader DC, the contents would be visable.  That is not an option anymore.  How do I fix?