A lot of these answers suggest some form of lamination, which is obviously the way to go, so I thought I’d chime in with my two favorite materials for bonding with tissue paper.
The first method is to use freezer paper. This paper, which is cheap and widely available in grocery stores, has a plastic backing that will melt and bond with tissue if you iron it on.
The second idea I have, which I’ve never used for sewing but I have for just about every other type of durable-paper needs, is to use a tissue-foil lamination.
For a commercial pattern where it’s already printed on a large pice of tissue paper, I’d lay out strips of tin foil (like grocery-store aluminum foil) in a width to match your pattern (you’ll probably need to join strips and can just use a glue stick to overlap joints). Then I’d roll my pattern around a packing tube to help you control it as you do the lamination.
The fastest and most fail-safe method is to coat the foil with a fine spray adhesive, then use the tube to roll your pattern across the sticky foil, which minimizes wrinkles when joining the materials. I would then flip it over and laminate the other side of the foil with plain white tissue paper for good measure.
If you are printing out your pattern and feel daring, you can actually run foil paper through a laser printer. You will get an extremely durable print that can be crumpled and deformed multiple times and stay readable. It is truly like a super-substrate.
To prepare foil for printing, cover both sides with plain white tissue paper and then be extremely conscientious about cutting down to size (using straight, square cuts). If you don’t laminate both sides, if you leave some foil exposed, if there isn’t a good bond between the layers, oversights like these can ruin or severely damage your printer (I know from experience). Otherwise, you can use this incredibly strong material to print a tiled pattern, join it together, and you will be amazed at how small you’ll be able to fold it (even to the point of crumpling it up completely) and how easily it smooths back out.