i am having a luau party and i have a question about invitations?!

You could attach a piece of clear fishing line and tape one end to the rolled up invitation and the other to the top of the bottle in order to make it that much easier . Sounds like a good idea too!

I would actually make the paper a half inch or more longer than the bottle and have it sticking out of the top. And/or punch a hole in a corner and tie a ribbon through it to hold it on or pull it out.
Another option is to make theater "stunt" bottles. Check on-line on how to make break-away bottles out of sugar, then they can melt it under water or crack it open safely.
Sound like a blast. Have fun!

you can put them in there, and also have them be easy to remove. you just need to tape the invitations closed while they're rolled up into little tubes. as long as the rolled up invitation is smaller than opening of the bottle, you're good to go.