We got some request about this issues from users.
So here is a small howto.

1) Create an image of your business card in your favorite program
2) Open the image in IrfanView
3) Select save as and then pdf
4) Set some ImPDF options
4a) In the "Layout" tab set the size of the paper you like to print to
4b) Set the page border
4c) In the "Tiles" tab select "RxC tiles, one image"
4d) Enter the number of rows and columns you like to use
4e) If there should be a distance between your cards add a tile border
4f) Verify that in the tile area you get the size of your business card
4g) "In the "Compression" tab check the quality (lossless is the best)
5) Save
6) Print the resulting PDF with your favorite PDF viewer.
Be careful to print without scaling the page