How best to store old legal documents?

[Stuving]

Many old legal documents (and some quite recent ones) are on a sheet of paper a little larger than A3, which is used as two pages side by side and folded. It was then folded into three (usually) and often put in an evelope for storage. What is the recommended way of storing these? Folding and unfolding them obviously risks tearing them, more so as they get old and brittle. Opening them fully flat needs a huge A2 portfolio (or something custom-made).  With a single fold they go in an A3 portfolio, which is more practical. I'm assuming they will be scanned in pages (foolscap or thereabouts) - even if this is a bit hazardous it reduces the need to look at the originals. So is it then OK to store them in their original folding? Any suggestions or references would be welcome.

[Lydart]

I'd unfold them as much as possible.   Keep original envelopes as well ...

I've got several large documents stored in the bottom of the wardrobe.  I started the pile with a sheet of cardboard, then a sheet of acid free tissue, then the unfolded document, another sheet of acid free, another card ... and so on.   IMPORTANT ... make a list of the pile so that you know whereabouts in the pile each one is !

Now to see what the professionals suggest ...