I doubt that the error you see is because of 32/64 bit issue. The error that you see i.e
vaja4.asm:(.text+0x7): undefined reference to `_printf'
is clearly telling you the symbol _printf is undefined which means that the library for printf function is not being linked.
your linking step i.e
ld vaja4.o -o vaja4
does not include any libraries. You need to link your program with a library that can provide definition of the printf function. I believe ld should pick the library it self without bothering you with these messages but because it is not able to find a suitable C library for this function, I guess you dont have the required libraries i.e either 32 bit or 64 library is missing.
Anyway, plz try the following sequence of commands to assemble and link your program:
nasm -f elf vaja4.asm
ld -m elf_i386 vaja4.o vaja4
./vaja4
