How to enlarge/zoom into a specific area in After Effects
You need to animate the anchor point. This is the point towards which an image will zoom if you increase its scale. So when you zoom in to the paperwork you have to put the anchor point under the paperwork.

Trouble is the anchor point is also the point at which the image is attached to the composition, so moving it will normally cause the image to move. After Effects has a tool call the "Pan Behind" tool , which deals with this problem. It moves the anchor point of a layer and at the same time adjusts the layer's position in the composition to match so that the layer doesn't move. To use the Pan Behind tool hit the letter y.

So to zoom in to one point, zoom out, and then zoom in to another point you need to first set keyframes for your position, anchor point, and of course scale properties. Do this at the time when your first zoom starts. With the Pan Behind tool adjust the anchor point (and thus the position as well) so that it's sitting under the papers, then animate your zoom in, and out.

The keyframe for your anchor point and position should be made "hold keyframes" so that they won't change until their next keyframe, at which point they will change instantly. Otherwise you'll have to set position and anchor points each time you set a scale keyframe (which would work too, but it's more work and harder to edit). Select the position and anchor point keyframes, right-click on one and choose Toggle Hold Keyframe from the context menu, or from the top menu by choosing Animation > Toggle Hold Keyframe.

Now go to the time when you want to zoom into something else on the desk. Use the pan behind tool again to set the anchor point (and position at the same time), then add scale keyframes for your zoom. Rinse, repeat.