After I finished compling an assembly I realize that the origin is off. Is there a way to realign the entire assembly as one?
If you have one of the part fixed, usually the first part in the assembly, right click on it and select float. Then you can use mates to align the assembly with the origin and planes any way you like. After they are aligned you can either leave the mates just the way they are or set one of the parts to be fixed again by right clicking on it.
That depends upon how you mated the components.
If all subsequent components are mated to the first component, then simply correcting the placement of the first component will do what you want.
If all components are mated to the top level ref planes you will have to adjust each independently. Or a quick & dirty workaround is to remove all mates, then use the Lock mate to lock all the parts to the first part, and then re-orient the first part.
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