Magnet sheeting may be made of PVC and cutting it in this manner may produce small amounts of extremely toxic chlorine gas. I am not sure. You do this at your own risk.
Step 1: Go Make Your Word File.
Open Corel Draw and make a text block the size of your scrap magnetic sheeting. My scrap sheeting was 3.5" x 24" and as such I wrote enough semi-random words to fill that space.
The text should be of transparent fill with a 1 pixel black outline.
For a better example download the attached work-file below.
Step 2: Print It Out.
Step 3: Wipe It Off.
Go wash the filings off your hands.
Step 4: Cut It Up.
First cut long strips between the lines of the words and then cut each word off the strip starting at one end.
Don't worry about slicing all the way through with the razor. The nice thing about magnetic sheeting is that you can score it and rip it very easily. A shallow score is more than enough to rip or bend a length of magnet cleanly in half.