I'm very new to Poser so forgive me if this is a basic question.

I have a model composed of several parts (body, eyes, teeth etc.).
Each part is a separate .obj file, so in Poser I'd like to import those files, and later pose those.

But I'd like of course that if I create bones on the body and I pose it, that eyes, teeth etc. would pose accordingly.

Is that possible or I have to merge all the body parts into a single mesh and then pose it ?

Import all the parts to poser. position them in place and parent the parts to the appropriate bodypart. Then open the hierarchy editor and check your figure. There is a button near the bottom to create a figure from your hierarchy.

You really need to have all the parts in a single OBJ file, otherwise you'll have breaks at the joins.
There is no need to weld the parts, Poser does this internally for body parts.

Quote - You really need to have all the parts in a single OBJ file, otherwise you'll have breaks at the joins.
There is no need to weld the parts, Poser does this internally for body parts.

Welding still works even if the geometries are loaded by separate 'objFileGeom' statements, rather than a single 'figureResFile '. The important thing is that the vertices in one part match up exactly (or almost exactly) with the vertices in the other part.

Attached above is the proof of the pudding. the file loads one box via 'objFileGeom', and the other geometry is 'geomCustom'. I could have used two 'objFileGeom', but then I would have had to distribute a separate obj file. Note that the two boxes in the figure are welded.