I think Bluejets was being funny, but he actually has a point:
You might try taking one of your purchased checks and covering all the references to the check number. I've done something similar by taping a small rectangle of paper over an item with invisible tape that doesn't show up on a copy.
Copy that on a good color printer. On the copy, carefully draw in the slots needed to enter the check number and you will have a "blank" check with no check number.
Copy the copy (on a good printer), and you have two blank checks. Repeat until you have as many checks as you can fit on standard size copy paper, probably 6 or 8: Now you can print your checks by the page.
You just have to remember to fill in the check numbers, carefully, so that a scanner can read the number. I think banks don't like it when a check shows up without a check number.