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In my opinion, you should be able to answer the question yourself. If an external assembly service provider is involved, you should ask him anyway about his requirements.
Generally, solder paste stencils are used for each side, that's intended for reflow solder. Wave solder of SMD parts most likely needs adhesive printing stencils, also two sided SMD may require large parts to be additionally fixed.
You might consider supplying paste mask for both sides regardless of what you "think" the vendor might want. this gives the vendor the ability to use whichever method of soldering that will suit your design.