emailed redlined word attachments appear as clean pdf documents

When I open up an email received on my PC computer that has an attached redlined "Word" document, the attachment opens up as a clean PDF. When I open up the same email on my IMAC, the attachment is the correct redlined "Word' document. The problem would therefore appear to be with the settings on my PC. Any advice aas to which settings need to be changed on my PC computer?