Open Property Management / Email & Printouts:
Choose the printout you want to edit and open Scheduling tab:
You will see three options:
1) Generate printout per each guest - this option has to be checked in order to be able to generate the printout for each guest
2) Fit one guest per page - check this option if you want to print the document for each guest on a separate page
3) Auto generate serial number - this option is connected with the key {GuestSerialNumber}. If you put e.g. 9 in this field, the next printout which contains the mentioned key will be generated with serial number 10.
After you have setup the printout, you can generate clicking on Print, directly in the reservation: