Your son is correct in applying for a new Canadian Passport if it is unreadable.
If you son is over 16 years he will need to complete the Adult Passport Application (Abroad) PPTC 040. The application needs to be submitted at the nearest Canadian government office where your son in located in Spain (Barcelona, Malaga or Madrid).
Spain – BARCELONA
Consulate of Canada
Address: Plaa de Catalunya, 9, 1§, 2¦ – 08002, Barcelona,Spain
Tel.: 34 934 127 236
Emergency toll-free to Ottawa: 00-800-2326-6831
Fax: 34 933 170 541
A guarantor is required to sign the application (someone known to your son personally for at least 2 years). If this cannot be provided a ‘statutory Declaration in Lieu of Guarantor? form PPTC 132 needs to be completed.
If the valid passport has been lost, stolen, damaged, destroyed or is inaccessible, complete a “Statutory Declaration” form PPTC 203.
It is recommended you either contact Passport Canada (Toll free: 1-800-567-6868 Canada) for more information before submitting.