My reverse order interpretation would be as follows:

User enters the values: 1 2 3 4 5 6 The output would be: 6 5 4 3 2 1

The code looks like this:

#include <stdio.h>
#include <stdlib.h>

int main()
{
   int i, num[6];
   printf("Digite 6 numeros inteiros.\n");

   for(i=0; i<6; i++) {
    printf("Digite o %d valor: ", (i+1));
    scanf("%d", &num[i]);
   }

   printf("Resultado:\n");
   for(i=5; i>=0; i--) {
    printf("%d\n", num[i]);
   }
   return 0;
}

First, your example does not compile because a } is missing. Look how it looks when properly indented:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i, num[6];
    printf("Digite 6 numeros inteiros.\n");
    for (i = 0; i < 6; i++) {
        printf("Digite o %d valor: ", i + 1);
        scanf("%d", &num[i]);
    }
    system("cls");
    for (i = 0; i < 6; i++) {
       system("pause");
       return 0;
    }

I suppose you have forgotten printf and } before system("pause"); . So this would be the code (printing in direct order):

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i, num[6];
    printf("Digite 6 numeros inteiros.\n");
    for (i = 0; i < 6; i++) {
        printf("Digite o %d valor: ", i + 1);
        scanf("%d", &num[i]);
    }
    system("cls");
    for (i = 0; i < 6; i++) {
        printf("O %d valor eh: ", num[i]);
    }
    system("pause");
    return 0;
}

You are reading the 6 numbers correctly. Then the solution would be simple. I have two alternatives, choose the one that suits you best.

Alternative 1:

Just print the numbers on the screen in reverse order. For this, you iterate the array (in the second for ) in reverse order:

for (i = 5; i >= 0; i--) {

Alternative 2:

You iterate the array in the correct order, but it fills it in the reverse order:

    scanf("%d", &num[5 - i]);

A recursive solution: -)

#include <stdio.h>
#include <stdlib.h>

void le_imprime(int n);

int main(void) {
    puts("Digite 6 numeros inteiros.");
    le_imprime(6);
    puts("");
    return 0;
}

void le_imprime(int n) {
    int a;
    if (!n) return;
    if (scanf("%d", &a) != 1) {
        fprintf(stderr, "Erro de leitura.\nPrograma abortado.\n");
        exit(EXIT_FAILURE);
    }
    le_imprime(n - 1);
    printf("%d ", a);
}

A pornographic solution (do not show it to anyone):

#include <stdio.h>

int main(int argc, char**allwaysnull) { int c;
  if( argc == 8 ){ return 0; }
  if( argc == 1 ){ printf("6 numeros inteiros.\n"); return main(2,NULL); }
  scanf("%d",&c);
  main(argc + 1,NULL); 
  printf("%d\n",c);
}

Update: By purist suggestion from @pmg, I've added the second main argument to (fraudulently) silence the -Wmain warning. The new version continues to be admittedly pornographic.