How do I add the same Modifiers to all Linked Duplicates? I am building a scene with a lot of leaves, a macroscopic view, each leaf is an object carefully placed rather than using a particle system. I have a base set of 12 leaves that have each been duplicated dozens of times as linked duplicates using Alt+D rather than Shift+D. Now that each linked duplicate has been carefully rotated, scaled, placed I want to add Solidify and Subsurface Modifiers to all of them but maintain them as Linked Duplicates. 

Is it possible to add the same Modifiers to all Linked Duplicates in some way?

When I add these Modifiers to the original object or instance it seems to Unlink it from all the Linked Duplicates creating a new object with the Modifiers. 

If this isn't possible to do as with Materials where a Material can be linked to an Object or its Data, is there a good workaround to achieve the same without unlinking all the objects and creating hundreds of new separate objects?
If you create a linked duplicate of an object (Alt+D) it will copy any existing modifiers. But the modifier stack of each duplicate can be individually manipulated without affecting the original. So if you retroactively add any modifiers to duplicates they will only be applied to one object.

You cannot add modifiers to multiple objects from the modifier panel. The modifier will only apply to the object selected last. However you can copy modifiers to a group selection, by selecting all the unmodified objects, and then the object with the modifiers, and use Ctrl+L to copy Modifiers.

Useful tip: to select all linked duplicates of a mesh use Shift+L or Select > Linked > "Object Data"





1st Image: Ctrl+L to copy modifiers from the last selected object

2nd Image: Shift+L to select all linked duplicates

S/O to @Ray Mairlot and @Gorgius for their comments, which I have redrafted as an answer for the sake of completion