I make and design greetings cards and I score the card to get a nice crisp fold, I use something called an embossing tool which looks a bit like a pen but with a ball on the end instead of a nib. You can get paper trimmers that have a scoring blade so that it doesn't actually cut through, but they can be a bit harsh if you only want to score paper. If you have a biro has completely dried up, you can use that and a ruler to score card/paper - hope this helps