What would be the best way to stick 2 sheets of acrylic?
I think that if I use some kind of glue, there may be a mark which can be seen if the acrylic sheets are transparent, unless if the glue has the same refraction index as the acrylic. Is this correct?
In any case, what glue would you suggest?
Thanks
Oooh, I was looking this up a few years ago for a project idea which I then abandoned. Let me see if I can find what I found then and put my old search to good use…
Use a 2 part Tensol , it fills gaps and creates a totally clear bond of high strength , its meant for joining acrylics. You must check whether its cast or extruded acrylic as you would need different for extruded. The secret to getting a totally transparent joint is to use a glue with a refractive index near to acrylic that fills all gaps , thin solvents wont do this and their bond strength is not good at all
I think that Tensol 70 is the glue he referred to, and I see Stykra A2000 advertised as a direct replacement.
No direct experience, just memories of looking for this half a decade or so ago. 
It seems I can’t find any of the references you suggest. What do you thinkabout this one ?
It says:
[Characteristics] - It is a transparent glue that is odorless, non-corrosive, not white, not brittle, not yellow, not hardened.
[Type of bonding material] - Ceramic, glass, leather, plastics, electronic components, metals, stone, rubber, wood, acrylic, etc.
Temporarily out of stock. 