Yes, there are strict limitations to how large your display can be. Here they are: http://societyforscience.org/isef/rules/safdisp.pdf
. They are very
strict about their display and safety rules. They have measuring tapes and will measure your board to make sure it is within the dimension limitations. They don't even let you have a binder or folder stick out over the edge of your table.
Choosing how you want to do your display depends on your budget and how you are going to get your display to ISEF. I would talk with your fair manager (or whoever is in charge of your ISEF delegation) to see what they recommend for transportation. As far as getting your material onto the board, if you go with large poster, you can design it in programs such as PowerPoint, Publisher, InDesign, and Illustrator. Companies like FedEx Kinkos can usually print them, although they are pricey. Other companies that do large color printing can often be cheaper, but harder to track down. I would look in the Yellow Pages for ideas about local printing companies. Again, your fair manager may have some suggestions. If you do a tri-fold board, you can choose to have things printed commercially, or you can do it yourself. If you have a nice color inkjet printer, you can usually do it yourself and make it look nice, especially if you use a few tricks. For instance, using photo paper instead of regular paper will make your images and text really "pop". Also, you can cut poster board to fit your printer. For example, say you had a section on statistics analysis that was 11 inches by 20 inches. If you find a piece of nice, quality poster board (I prefer to use white and then print color in it), you can cut it to this size and then feed that long piece through your printer (assuming it will accept something 11 inches wide). This is a good way to print long sections continuously by yourself. You will need to mess around a bit with the settings on your printer, but doing so will usually save your some money.
I've attached an example of one of the spreads from an old ISEF board of mine to help you see one possibility for designing a tri-fold ISEF board.
Let me know if this is confusing or if you have any more questions! We're here to help!