Seating charts printed on.....

I've seen them printed on poster board.

What do you mean expensive? If you're putting it in a frame then i'd just choose the heavy duty paper so that there are no wrinkles. I can't imagine an 18x24 would be anything over $100 to have printed even for a canvas.

The seating chart (pdf) was $40 and then the photo shop wants $70 to print it. It's the size of a poster, 24" x 36" so I bought a frame to put it in

Are you you putting it in a frame? I had a welcome sign printed on 100# cardstock at Office Max (or Depot, whatever) and then mounted on a foam board. Cost 24 bucks. Looks great. It would be even cheaper if not mounted on foam, which you wouldn't need to do if you're putting in a frame.

Check out vistaprint. I print out posters of our vacation pictures all the time and very reasonably priced.

My florist told me to have it printed on posterboard

I ordered the PDF from a shop on Etsy (the woman is a graphic designer) and she plugged all of our guest names into the file and had mine printed at Staples. I had it printed on a foam posterboard which will be displayed on an easel.

I'm getting mine printed on a 16x20 canvas. I called staples, office depot and walmart and thats what they all recommend. I also messaged the etsy seller that I'm getting the digital copy from to ask if this would work since the listing says to print on heavy cardstock and she said yes. She said to print on heavy cardstock if you plan to frame it or a canvas if you plan to set it on an easel