Question:
If I scan my fishing license and save it as a pdf file on my smartphone, can I then just show my license saved on my phone to any game warden who asks to see my license?

Answer:
No, you are required to have your actual sport fishing license in possession while fishing (California Code of Regulations Title 14, Section 700 and Fish and Game Code, sections 1054.2 and 7145(a)) and to present your actual license upon request to any game warden who asks (FGC, Section 2012). Fishing and hunting licenses are printed on special waterproof paper to prevent fraudulent duplication. A scanned or digital version of your license on your phone could be easily altered from its original image.