It can be done and it's really a job for a service engineer unless you are very methodical and experienced but here are a few pointers you may over look, the main issues will be with the locking mechanism
1, The flying mullion MAY be a offset type so has to be flipped over rather than just moved left to right or right to left? Mark with a pencil line before removing as this NEEDS to go back at the right height, it could also potentially be screwed on from the glazing side so the slave door will need deglazing to access the 5 fixing screws, you will then need to re toe and heel the door afterwards
2, If you have separate hook keeps they will certainly need to be repositioned and the pvc will need re routering out to accept the hook boxes. See 3 for the centre latch plate
However if you have a one piece locking strip on the slave door which matches the locking mechanism on the master door then it can't be just moved from left to right because the latch will be facing the wrong way, if you invert the locking strip then the latch whilst will be facing the right way it will be upside down and below the deadbolt which now won't match the locking mechanism on the master door so you will need a complete new mechanism and matching locking strip
3, If you have a separate centre latch plate it will need replacing as these are handed and can't be flipped over otherwise it'll be upside down
4, The spring latch in the master door will need reversing
5, Split the shoot bolt extensions from the slave door mechanism and remove the mechanism and transfer to the master door and reattach the shootbolt extensions, the top and bottom shootbolt keeps may potentially need repositioning afterwards
So unless you are really brave then I'd leave this to a service engineer and even then it's going to be a good half a day's work but at £80 + vat per hour minimum and £100ish + vat for a new mechanism your getting close to being it being cost prohibitive
If there's any other service engineers or fitters here then let me know if I've missed something