As you can see the left side of the scan is brighter then the right side. You have two options.
1) Make the right side brighter or
2) Make the left side darker.
I've chosen to make the right side brighter.
Step 2 --> Go to Layer --> New Adjustment Layer --> Brightness/Contrast.
I'm going to use a brightness of 15 myself.
Now that everything is in tone with each other, we can focus on the rest.
Step 3 --> Fix the background with the 'Healing Brush Tool.'
Make sure it will look similar to this.
We're going to do the same with this guys' suit.
Step 4 --> Use a soft-rounded brush for the suit. (You get a soft-rounded brush by changing the opacity of 'hardness.')
Step 5 --> Start with it like this example below.
Step 6 --> For the places where you have to work more precisely, change your soft-rounded brush back to a hard-rounded brush.
Keep repeating this over and over and don't forget to make a different selection each time.
Step 7 --> Don't forget to clean the shadow down there.
When you're finally done it should look similar to this.
Step 8 --> Straighten, re-draw as much as possible and then rotate the page.
The final outcome is like the example above. And as we can see the right side of the guys' suit is too bright compared to the left side.
Step 9 --> Level the right side of the guys' suit so it will be in tone with the left side.
*Note: The suit isn't suppose to be completely dark! So don't level too much!
Step 10 --> Check the page for dust, shadows, and weird lines that aren't suppose to be there.