I had the same issue after I removed reader from my computer. to fix I
control panel >programs and features > selected adobe pro > change > and repair option
The preview tab is 'missing' where adobe LCDesigner is installed but Acrobat Pro (or Reader) is not installed.
SOLUTION: You must install either Acrobat Pro (or Reader) -- then LiveCycle will show the preview tab.
NOTE: Third-party [non-Adobe] PDF software will not 'play' PDF or XFA forms (this is another related reason the Preview Tab maybe missing)