I suppose that you don't have space around your document, or don't want to use some. Then your only solution is to display the action button on the document.

You chose to show an icon on mouse hover, probably in order not to cover the document unnecessarily. This is fine but be careful as tablet touch screens don't have hover events.

Another solution is to have a sliding toolbar, that shows when clicking on a small icon. This spares space if you have more than one action button, but doesn't make much difference if you have only one.

I suppose that you don't have space around your document, or don't want to use some. Then your only solution is to display the action button on the document.

You chose to show an icon on mouse hover, probably in order not to cover the document unnecessarily. This is fine but be careful as tablet touch screens don't have hover events.

Another solution is to have a sliding toolbar, that shows when clicking on a small icon. This spares space if you have more than one action button, but doesn't make much difference if you have only one.

Edit: if you need to unselect your option, you clearly need a toggle button or a checkbox. There are many ways to render this, it depends on your overall design.