Like others have said above, I use Zip-Loc bags. If I had to keep bigger documents (A4 or letter size) safe without folding them, I would go to a marine chandler's store and buy a Zip-Loc packet that is sold to sailors for the purpose of keeping marine charts dry on sailboats.

I'd like to add one further suggestion to this discussion about documents:

Don't store your documents (ownership, insurance, etc.) in a place that is 'quick and easy' to get at. Instead, store them deep inside a saddlebag, way at the back or bottom, in a place that will take a minute or two to get to, and require you to remove a few other packed items to get to the documents.

I say this because the only time we ever need to produce documents is if and when we have been stopped by a police officer or customs officer. Storing the documents deep inside a saddlebag creates a situation where the police officer or customs officer has a minute or two to 'cool down and assess you better' while you dig out the documents for them.

I have found that this extra minute or two (which is usually spent in silence, as you dig out the stuff) often results in a significant change in attitude of the official... they get a chance to look you over, see what you are carrying in the saddlebag, come to the conclusion that you are a pretty inoffensive citizen, and subconsciously, they often feel a wee bit 'obliged' to you as a result of having made you tear everything apart to get the documents.

The result of this is that conversation is usually a lot more cordial and less confrontational once you do produce the documents, and the officer concerned is usually in a more pleasant mood when they look over the documents, because that one or two minute delay has enabled them to break out of their usual 'confrontational' frame of mind that exists whenever they stop a vehicle for inspection.

Michael