You failed to say in you post whether these doors were interior or exterior. With interior doors you first need to determine how you want these to work. For example do you want one door to be stationary with one active or would you like to be able to open both at the same time. Also whether you want to have a locking function on it. In a typical installation where one will be active, one door is made stationary by using flush or surface bolts to secure it and a passage or privacy lock is used on the active door. A pair of dummy knobs are placed on the inactive door to balance the look. When both doors are to be active but without a positive latching device, a roller latch can be installed at the top of each door and then either a pair of dummy knobs can be installed on each door or passage locks without drilling for the latches. There is another alternative (but much more expensive) is to use a pair of cremone bolts to make each door latch. This is high end stuff but very elegant.