Cloud, as a character, has difficulty edgegaurding safely compared to many members of the cast. However, he has some tricks up his sleeve. Reading air dodges with Cloud is essential. Most people typically air dodge near the ledge, since it's usually a safe option. To counter this, you can wait for the air dodge and punish with limit side-b, which is safe since Cloud doesn't fall when using it, nair, since the move is really fast and has decent knockback at high percents (make sure your double jump is still there when you use it though). If you want the crowd to go wild, you can punish an air dodge with down air (same thing applies with nair, since down air stays out so long). To set up for the down air, you can do a down throw near the ledge, wait for an air dodge, and spike your opponent. At earlier percents, try conditioning your opponent to air dodge via down throw --> bair, down throw --> up air, and down throw --> nair. I wouldn't suggest limit neutral b, since it's slow and obvious. F-air is also too slow and laggy, so you should use back air or nair instead.
Conclusion: Cloud relies off of air dodge reads for effective edgegaurds, and should save his double jump since his moves last a while. I hope this helped.