The filename, directory name, or volume label syntax is incorrect.

#include <stdlib.h>
#include <conio.h>

int main (){
    system(""C:\Users\Adam\Desktop\pdftotext" -layout "C:\Users\Adam\Desktop\week 4.pdf"");
    _getch();
}

cd C:UsersAdamDesktop;
pdftotext -layout "week 4.pdf"

//system(""D:\test" nospaces "text with spaces"");//gives same error as you're getting
system("""D:\test" nospaces "text with spaces"""); //ok, works

system("cmd /S /C ""D:\test" nospaces "text with spaces"""); //also works