There are a few tabs for this song but none are 100%. This is exactly what Imagine 
Dragons plays on the acoustic guitar in the studio version/live performances

CAPO 5
G
If you love somebody
C
Better tell them why they?re here ?cause
D                            Am7
They may just run away from you
G
You?ll never know quite when, well
C
Then again it just depends on
D                             Am7
How long of time is left for you1
G
I?ve had the highest mountains
C
I?ve had the deepest rivers
D
You can have it all but life keeps
Am7
moving
Em                        D
Take it in but don?t look down

                         C
?Cause I?m on top of the world, hey
                  G
I?m on top of the world, hey
                      D
Waiting on this for a while now
                       Am7
Paying my dues to the dirt
                      C
I?ve been waiting to smile, hey
                         G
Been holding it in for a while, hey
                    D
Take you with me if I can
                              Am7
Been dreaming of this since a child
                  G
I?m on top of the world

G
I?ve tried to cut these corners
C
Try to take the easy way out
D                             Am7
I kept on falling short of something
G
I could of gave up then but
C
Then again I couldn?t have ?cause
D                               Am7
I?ve traveled all this way for something
Em                         D
Take it in but don?t look down


                         C
?Cause I?m on top of the world, hey
                  G
I?m on top of the world, hey
                      D
Waiting on this for a while now
                       Am7
Paying my dues to the dirt
                      C
I?ve been waiting to smile, hey
                         G
Been holding it in for a while, hey
                    D
Take you with me if I can
                              Am7
Been dreaming of this since a child
                  G
I?m on top of the world


Ohohohohohohoh ohohoh (x2)


                         C
?Cause I?m on top of the world, hey
                  G
I?m on top of the world, hey
                      D
Waiting on this for a while now
                       Am7
Paying my dues to the dirt
                      C
I?ve been waiting to smile, hey
                         G
Been holding it in for a while, hey
                    D
Take you with me if I can
                              Am7
Been dreaming of this since a child

C
And I know it?s hard when you?re falling down
           G
And it?s a long way up and you've hit the ground
        D                   Am7
But get up now, get up, get up now
(Played a second time then continued through the next chorus)


                         C
?Cause I?m on top of the world, hey
                  G
I?m on top of the world, hey
                      D
Waiting on this for a while now
                       Am7
Paying my dues to the dirt
                      C
I?ve been waiting to smile, hey
                         G
Been holding it in for a while, hey
                    D
Take you with me if I can
                              Am7
Been dreaming of this since a child
                  G
I?m on top of the world

G G G G