PDF Preview Handler add-in for Windows Explorer, Microsoft Office, and Outlook automatically configures itself to preview a PDF file in the Preview pane of Windows Explorer or in the Reading pane in Outlook 2013, 2010, 2007. Thus, you can preview PDF document in Windows 10 without opening. The freeware program installs a PDF preview handler add-in and shows a thumbnail preview for icons and also the icon changes to the one from PDF Preview.