Someone in my office just had this issue, and it was because one of their previously opened files reliably caused Preview to hang when opened. Unfortunately, whenever they opened Preview, it automatically opened all windows that were open when it was last terminated, causing it to immediately hang.
To fix this, we permanently disabled the feature where Preview automatically reopens previously-open files, using the command suggested at https://apple.stackexchange.com/a/54856/51010:
defaults write com.apple.Preview ApplePersistenceIgnoreState YES
After this, he was able to open Preview without it hanging.